The Offshore Voyaging Reference Site

Smartphone (CrewWatcher) or AIS-Based Crew Overboard Beacons?

OK, might as well be up front about it, I’m thinking that smartphone-based crew overboard (COB) beacons, like the CrewWatcher™, have got to be the worst idea I have heard of in a very long time, particularly since we already have a much better alternative: AIS/DSC beacons.

In fact, the only reason I can come up with for why the former are even a thing, is that it is a manifestation of the smartphone addiction syndrome that many people have been worrying about lately. In this case the symptom seems to be:

I will buy anything, no matter how ill conceived, as long as it runs on my smartphone, and even though there’s already a much better alternative available.

That was sweeping. Let me go through my thinking, and compare the two systems.

Update October 2021

It appears that CrewWatcher have gone out of business. Normally I don’t wish business disaster on anyone, but the CrewWatcher was such a dangerous, and yet clearly seductive, product that I’m hugely relieved that it is no longer sold.

We will leave this article up since it explains how ideas no matter how stupid can still gain traction and how important it is to exercise our common sense around boat gear and particularly marine electronics.

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Rick Samuels

A locater based on Bluetooth is a horrible idea. My high end phone (Pixel XL) doesn’t always automatically connect with my car’s Bluetooth setup which is less than three feet away. The idea of trusting my life to this technology is akin to using a clothesline to haul myself up the mast. It might work, but the consequences of failure are severe. The only valid use I can think of would be to supplement a tested AIS/DSC setup.


I never EVER said they should replace AIS beacons for offshore boats, and in fact Isbjorn has an AIS beacon in each of our 8 onboard PFD’s. The Crewwatcher is marketed to the masses of inland & coastal cruisers who are never going to spring for an AIS beacon, and I think are better than nothing. It shouldn’t be a comparison, they’re two different products for different markets. They’re alarms, basically, and they work in that capacity and I think can be useful (they can even be stuck in the bilge as a wireless high water alarm with their water sensor). Please make it clear that I am not in the smartphone camp on this one and never was.


Alright, here’s how I really think about this. I did, and do, recommend the smartphone solution – specifically the Crewwatcher – in certain instances (which I’ll get to). I never said they should replace AIS beacons.

Take Chesapeake Bay boaters, for example, who may never give a second thought to safety items. How can something like this, a simple, familiar solution at a reasonable price, NOT be beneficial in some sense, even if it just gets them THINKING about safety in a way they hadn’t before? I even said on the Crewwatcher site that “Perhaps most importantly, the device keeps the crew thinking ‘like a sailor’ – the best MOB safety is prevention, and just having the device in your pocket reminds you of the consequences of falling off the boat.”

John writes kind of the opposite – “As I look at it, my first concern is that wearing one of these beacons may give crew the impression that their chance of survival if they go overboard has been substantially increased.”

Maybe I’m being too optimistic, but if I am, I think John is being too pessimistic. I can’t see how encouraging safety on a masses level isn’t beneficial to the whole culture of sailing (but I understand the argument).

In reality there IS two different markets – the inshore market is never going to equip with AIS beacons on a large-scale level – heck, a lot of inshore boats don’t even have AIS!

Now, that said, using these with an actual smartphone isn’t the best way – instead, use an iPad plugged in to power, and connected to the ship’s audio with an aux cable, not bluetooth. Understand the tracking limitations, think of it as an alarm, and THINK about MOB prevention in the first place.

I still think this has to be better than nothing at all.

Robert C Shook

Jon, I think you’re missing the MOB alarm functionality.

I agree that these devices shouldn’t be advertised as aiding in recovery using location data, but I do think the alarm feature is an innovation.

Even my on-watch crew going overboard triggers my CPA ais alarm, it’s going to have to go off a number of times before I get up to see what’s going on.

I also think an edit in the article to clarify Andy’s position is warranted.

Rob Gill

Ok – here is the argument from a electronics industry point of view – it’s the business case of “good enough”. Remember when police forces all carried emergency “press-to-talk” radios, quite large and clunky and very obvious in use? Now, many (not all) particularly plainclothes police men and women will use their mobile as it is so much more mobile, way more covert, cheaper to own / operate and has far superior data capability. In some cases mobile even has better coverage. Ditto taxis, trucks, busses etc. At some price point, “good enough” sees a wholesale leap to a new technology platform with substitution of the old, and mobiles have been at the forefront of this with many industry applications (including marine charting). But for public safety, particularly fire services, press-to-talk remains the gold standard, as a “good enough” approach can cost lives when it goes bad. I think your excellent comparison above has many parallels to this.
So when does “good enough” become acceptable? Personally I agree that Blue Tooth is a very limited technology to use (since I have problems using it with my boat stereo) but as Andy reasoned in his reply, it could have a “good enough” place in inshore boating. Time will tell, as I am sure it will be adopted by many.
Equally, I would expect overtime the competition it provides will at least reduce the price point of AIS and Satellite based personal EPIRB options with their added “sails tax”, so that can’t be all bad, eh?

Joerg Esdorn

I recently had the occasion to try out a smart phone based alarm system on a long transatlantic voyage. I fully subscribe to John’s views expressed above: they are toys and the big problem with these things is that they are bluetooth based, which is not a reliable system. We had a large number of false alarms – usually during the middle of the night. We also had two of six units never working at all! We tried all six units on land and four of the six went off once the person carrying it was about 100 m away from the boat. The other two never went off!! We called the manufacturer and did some troubleshooting with the two but they never worked at all. Truth be told we also had one of the Spinlock/MOB1 units go off unintentionally a few times – but that was probably because we did not install the little protective cover plate over the MOB1 trigger as recommended by the manufacturer. We had too few of those on board. When the bearer of the vest moves a lot on board, the unit can trigger automatically.


I’m 99% sure these are able to integrate with other PFDs besides Spinlock. I’ve found the new Crewsaver PFDs more comfortable than Spinlock, but they’ve all got the same specs, so it’s a personal preference (if you get the right model). But just to be clear.

Rob Gill

Hi John,
For completeness, let me illustrate my “metaphor” with an example. During the 2005 London bus bombings, many public agencies and businesses had ditched their dedicated radio networks for public mobile services that were more useful, less costly and more mobile. But when the attacks happened, within minutes their wonderful mobiles became almost useless as a terrified and concerned London public flooded the public networks with texts and calls to family and friends. A more cautious organisation that retained their dedicated radio network was London Bus. Even though they were the most directly affected party, their dedicated press-to-talk radios worked right through the crisis enabling critical command and control functions to continue and providing crucial support to staff and customers during the emergency, then afterwards to help people get home safely. My point simply being that “good enough” works to a point, often brilliantly, but when it suddenly doesn’t, there can be major consequences particularly when safety is an issue.
So, again from an industry point of view, “good enough” solutions need to make sure that their adoption and their limitations are understood and not over sold. But I could suggest the same be said for many other devices such as AIS beacons vs personal EPIRB, life preservers vs life jackets, LED flares vs parachute flares to name a very few.

Serge Paul

To me this is a No brainer, better than nothing should not apply.
Very good writing.
Tanks again John.

Dan Manchester

I would like to think that the next logical evolution of the AIS beacon is to integrate it with the functionality of bluetooth. Add a bluetooth link to smartphone to allow constant monitoring (battery, condition, link state) and auto deployment when wet, whilst still providing the capabilities of AIS once in the water in an active POB situation. Couldn’t be that hard, surely.

Matt Marsh

I kind of like that idea. Use Bluetooth Low Energy so it doesn’t run the batteries flat on a daily basis, and have each unit just spit out its serial number and self-diagnostic report when polled.

Using Bluetooth as the active / primary link in any kind of safety-critical system is the kind of “tier-one moron” move that’ll make the engineering manager shuffle you off to something nobody in the company cares about, like maybe writing user manuals. Bluetooth is a versatile and very useful protocol for low-cost, low-criticality things, and works great as long as you keep its substantial limitations in mind.

Safety-critical data needs to use a communications stack designed for the conditions it will encounter. There’s a reason why your car’s stability control computer talks to the sensors and the brakes over CAN rather than 3G cellular. And there’s a reason why distress beacons use VHF AIS/DSC instead of WiFi or Bluetooth.

Stein Varjord

Hi John.
Sorry for writing such wordy pieces, but I think I can’t stop it. I’m a wordy guy and going into detail might make it easier to see why my statements are valid or not, sometimes….

As all previous here, I totally agree that the AIS beacon is the way to go and that a phone based alternative can only be a highly compromised low end alternative, at best. The topic of psychology has been mentioned. I think that topic might need some more attention. Mainly because it affects us in several “sneaky” ways.

An example: If I have to go on deck at sea in severe weather, which I try to avoid, I’d like to wear a harness, a vest and an AIS beacon. As most here would agree on, the harness is the most important item. If I had no beacon, I’d also choose to not wear a vest, because the vest alone would not increase my survival probability noticeably if I fell, and I know for a fact that the vest will lull me into the feeling that I’m kinda safe.

I’m extremely critical to the attitude most normal boaters and the authorities have to “Safety” vests. I think it’s a dangerous hype, close to a flat out lie. I think that in normal boating, vests may even cause more deaths than they save. Statistics from Norway before and after wearing a vest became mandatory, indicate this. Even with that opinion and critical attitude, wearing the vest will quite strongly affect my own feeling of safety. I’ve tested it loads of times. My own intuitive attitudes do change a lot. This thing hugging my neck, with the serious steel rings I see dangling on my belly, they make me feel like I’m serious, competent and taken care of.

This feeling will inevitably make me change my behaviour. The small detail decisions will be a bit different. Where I put my hands. How low I crawl. Which tasks I think are safe enough to do or not. Lots more. These small details add up to a much changed risk of something bad happening, like falling. I’m a human and happy that I have feelings, but prefer to be aware of when I can be trusted and when I can’t.

So back to the trip on deck. If I had no harness, I might consider not wearing any other safety item either. If I did wear a beacon and a vest, it would be only if the boat had a competent crew ready to act quickly. If doing maneuvers was impossible, say in a serious storm with huge waves, why would I wear a vest and beacon? Why reduce the awareness of grave danger if it doesn’t reduce the danger level? They would know where I was, but not be able to go back.

As you probably have guessed, I think the phone based systems will have a similar effect. They’re not intended for going on deck in a storm, of course. If they have a function it must be either track your position, which they can’t, or alarm others on the boat, which means it must be a boat with below deck facilities. A pure alarm is more useful in inshore boating, where one can normally see a POB quite far away, as opposed to offshore. But still, is it worth the deterioration of danger awareness?

Andy, you say it might make people aware that they need to think about these things, which I agree might happen, but assuming the target group here are people in need of this type of education, wouldnt they see the app as having properly dealt with the POB safety issue? Wouldn’t they be thoroughly influenced by the false impression of safety, which will inevitably make the actual risk behavior get worse.

Some of them will probably even think they now have an ocean ready vessel with their “high-tech” gadget and go offshore into some serious weather. I’m sure the gadgets have warnings of limited functionality, etc, but so does all electronic charting systems for amateurs. The plotter maps and software all say things like “for planning only. Must not be used for navigation without other charts.” That’s wise but still bullshit. We all use them for full on navigation, of course. The less experienced will happily think they’re in cohorts with the cool ocean sailors.

I think the phone gadgets are made because they can be, not because they’re good. A phone has that functionality, the gadget is cheap to make and seems cool, so it will be sold. Good enough, but just for those reasons, I think… So in my mind, these phone systems are total crap with zero usefulness and might fall into the well meant safety hypes that end up killing more than they save.

Stein Varjord

Wow. Thanks for the praise!
Reading through my own post again I notice how I could have gotten mostly the same message through in maybe half the words, which would still have been a quite long post… I think you know your way around words pretty well too, (!) so I think if you wrote about the same topics, you’d do at least as good a job and probably keep it tighter and while at it, get some more angles than those I thought about.

This is one of the great advantages of the format of this site. Many different people with much experience give their takes on a topic. No matter how well something is thought and written, some readers will miss important points. With the discussion afterwards, the understanding becomes greatly deepened for everyone, partly because new thoughts come, but maybe more because the same is seen from different angles. Actually, writing my take on anything also makes me understand it better. I love this way of learning!


Hi Stein,
Good text you wrote. If I may, I would like to add my non-informed and not statistically verified opinion on wearing safety vests on sea.
– Personally, I use Baltic offshore 50N flotation vest, because I do can swim, it warms nicely, I can (and do) hang embarrassing amount of gear on it, and it has an inbuilt harness with marginal crotch strap (I can sew better straps on it if i wish, but I don’t…) and it doesn’t blow up accidentally, works because of Archimedes not by willingness of salt plug and gas, and doesn’t hamper my movement on water with kaboom-mega-dollyparton effect…
– I would recommend using safety vest to anyone, and even demand it on some occasions. It provides a naturl place to hang strobe light and whistle, has reflectors, and has a sprayhood that prevents drowning by waves. (see that linked Clipper race MAIB report, the second case was probably a drowning on surface). And some mates are already frightfully skinny for flotation purposes (if you catch my drift. “The 50N force is strong with this one”) (Some are not)
– On my limited experience, accidents happen because of: Haste, fatigue, distraction, miscommunication, misunderstandings, difficulty to see/hear/to be heard, equipment failures, sudden movements, etc – and I’m not really sure if it has much additional effect here if they have vests on or not.

Stein Varjord

I notice that my post may seem like I think safety vests are useless. That’s not so. I should have explained better. If I’m already overboard, there’s no doubt that a vest will keep me alive very much longer, with a better chance of rescue.

What I mean with calling the vest a hype that may kill more than it saves is that it’s being promoted brainlessly as if you can’t die if you wear one. Lots of average boaters have a feeling of safety that is not true. Even coastal cruises in the summer mostly go far enough from land to make it unlikely that one can swim to land even with a vest, so one needs to be rescued by a boat, which is very far from a certain thing. Especially since people fall overboard mostly in wind, waves and possibly darkness. Offshore the probability of being found is often close to zero. I’ve done some testing with a very ambitious oceangoing racing monohull with a 6 man athletic crew prepared for the task and fairly easy conditions close to land. Mostly failed to recover the POB. Made us much more careful.

My point with calling vests a dangerous hype, thus, is not that they don’t work. They certainly do, but that they really do change our feeling of safety and that really does change our behavior. We are actually at a considerably higher risk of falling overboard when we wear a vest. My guess, and numbers from one year confirms it some, is that the survival improvement of the vest doesn’t outweigh the increased number of falls due to people being people.

I also use vests, mostly also non inflatable ones, because I mostly used to sail boats that throw me in the water if I do a small mistake. Formula 18 etc. I do also use an inflatable one, because it has a harness, but I have removed the salt tablet because I don’t want it to be automatic. I’ll pull the line if I want to. Very easy. The automatic feature is useful in very unusual cases and causes danger way more often. It almost killed a friend of mine because it threw him into cold water and prevented him from climbing out on a stern ladder. The total safety is better without automatic release.

I really think vests are important to have, and to use, but only the right way, in the right context, with knowledge. Pushing it hard as some countries do with even legislation, like Norway, and calling it SAFETY vest, undermines safety. Safety comes from inside our heads, and cannot be bought in a shop.

Charles L Starke

Dear John
I am not sure that answers all the questions about surviving a cold water immersion. A life jacket helps combat the “cold shock” response of gasping for one minute with initial lung intake of water, and then the weakness from cold water immersion. “Cold Water Boot Camp” addresses these concerns and problems.

One might then deflate or take the life jacket off to get in a dinghy or climb a ladder.
Best wishes,
s/v Dawnpiper

Stein Varjord

Getting quite deep into a side track here now, but just a short one this time. 🙂
At the safety course I’ve mentioned, we wore top quality inflatable vests and were instructed to fill our lungs and hold our mouth and nose firmly blocked with a hand to stop the gasp reflex. It’s not possible to decide not to do it.

The vests take at least some seconds to inflate. In pretty much all scenarios of a POB the head will be immersed in the first stage of the incident. The vest will be of no help in preventing inhaling water at first.

My friend who nearly died tried to get the vest off, but didn’t manage. February in Oslo meant useless fingers in seconds. Deflating was impossible for same reason. Ridiculous tiny thing to press to get it way to slowly empty. All the time desperately trying to get up a ladder.

He had a knife and tried to get to it. Due to the vest being in the way, and stiff fingers, he lost it. By now he was scared and so cold he was getting confused. We were close by on a pier calling him to come closer, but he couldn’t figure things out. We got hold of him with a boat hook from a moored boat. He barely made it.

He and all around were very skilled boaters. He worked full time for my sailing club. No alcohol was in the picture. Lesson learned: No way will I ever have a vest with automatic inflation!

Myles Powers

A well deserved rant! I’m sending note to Apple. Let’s make sure it never makes it to the App Store ;->


For those who know diving, this phone-beacon thingy reminds me of the “spare-air”.
Useless, more dangerous as gives people who havent thought the problem through a false sense of security.
IF you really want an alarm, maybe the ray marine tag is better? While i would put this one in the same category as well due to range. At least doest rely on an phone alarm. Not sure if they still sell them anyway.


Interesting debate. 20 years ago I went into the drink at night while climbing from my dinghy to my vessel anchored on a fast moving river. The crew was below. I was quickly swept away, swimming toward the boat had negative results. Shouting didn’t help. Luckily there was another boat downstream. I mentally calculated my set and drift and found refuge there. It was scary. Did I have vest on? No. That was dumb. If I had a Crew watcher in my pocket the possiblity of the crew being alerted would have been greatly increased. That’s the kind of “good enough” that makes sense. Think of this. My year 3 old grandson is on board. He’s wears a vest, even at dock. I keep my eyes on him all the time. Until I don’t. How many kids drown in their backyard pool when parents lose track. A Crew Watcher wouldn’t relinquish my responsibilities, it fortifies the chances of a positive outcome in case of an accident. Is Bluetooth reliable? Nope. ANY gizmo that has electrons running through it can crap out. That’s a given. If there is overpromise implicit in the product, it should be pointed out – thanks John. Is it an affordable system for those who want some kind of peace of mind functionality? Andy, you’re on point. I simply go to the product’s name to make my case. It’s not Crew Tracker or Crew Saver…it’s Crew Watcher. All this said, I have a Crew Watcher waiting for me on back order. This discussion has made me think if this system is for me. Hmmm? Thank you AAC.

Marc Dacey

It would not occur to me to have a Bluetooth-mediated device for safety purposes. I’m aware of its severe limitations: my brother-in-law devised a subway train locator system premised on Bluetooth that required hand-off transceivers every 30 metres in the tunnels because Bluetooth is weak and range-limited. But I am also one of those inland sailors who’s had a PLB for a decade and will be getting AIS tags/beacons as I’m putting in a Vesper XB8000 by spring and already have AIS receive on my VHF. In addition, the stress of RYA COB procedures (and I’m aware there are mixed feelings on RYA training in this crowd) is on spotting and tracking COB manually.

Although I am gravitating toward the use of Wi-Fi for outside “repeater” displays, having been pleasantly surprised that they work functionally from inside my steel pilothouse, I consider smartphones purely auxiliary conveniences. Tablets, being more powerful, occupy a middle ground; a tablet wirelessly acting as a repeater at our outside helm (and firmly waterproofed and secured) could allow me, for instance, to see the AIS beacon and the course to steer from our aft deck, which is a metre higher than our pilothouse helm. That’s a real advantage. It seems to me that the baseline issue is not frankly evaluating the benefits and the limitations of new technologies in light of intended use.

Bluetooth headphones on land? Fine. Failure is inconvenient. Bluetooth systems on board? I have a wee JBL speaker on a carbiner that’s Bluetooth-enabled. I can’t get it to send streams of Andy’s podcasts to the foredeck from the pilothouse before it cuts out. It’s why I download them to listen on wired headphones on, yes, my smartphone. Bluetooth was not meant to accomplish that. It was meant to replace a one-metre wire.

Todd Huss

Excellent piece of writing. I make my living building apps for phones and tablets and I prefer them for just about everything on the boat over the mfds I have. So I am usually in the “want it on my phone or tablet camp”. However, in MOB situations AIS beacons with a dedicated AIS display are the ONLY reasonable solution on the market for passagemakers at the moment. I like having a dedicated AIS transceiver/display for this reason but now that many VHF radios have built in AIS receivers and displays it’s even an accessible safety solution for cruisers on a tight budget.


Just FYI, the standard horizon GX2000 is simply a vhf receiver with AIS DISPLAY (requiring AIS and GPS input). For a hundred bucks more the GX2200 is a VHF with AIS receiver and built in GPS; therefore allowing full AIS receive and display functionality without any connections to other equipment.
Also a small side note, I believe the GX2000, without gps connections allows/requires you to input your gps coordinates manually for the DSC notification.

Marc Dacey

Correct. We have the GX2200 and it works impressively well: we can see AIS targets at 10 NM, even other Class B boats. We are installing a Class B transceiver this spring, so the AIS function on the VHF will be back up, but I have to say that even in our limited use of it, having AIS data has been a real enhancement at the helm. We will probably link our Vesper XB-8000 wirelessly to our B&G plotter (both are inside the pilothouse) and the GX-2200 via a dongle to our standalone Furuno radar. Throwing in AIS PFD tags into that mix, which could be seen then via plotter, laptop and radar, would have a lot of bases covered and redundancy secured.


Most of the comments here agree that Bluetooth and mobile based solutions are never thought for offshore, but for my opinion too many of the commenters believe it may be “good enough” or “better than nothing” which I strongly (REALLY strongly) object. It reminds me on a parachuter having an umbrella to use when the main chute doesn’t open, I doubt he would say “well, better than nothing” while he races towards the bottom.

Being professionally employed in the telco/IT business I havge my daily encounters with the limits of mobile technology. The hardware built into mobile devices is never, ever, designed to cope with a hostile environment, and absolutely not designed to perform reliably in every instant. These thoughts alone should deter any boater, offshore as well as inshore, from using mobile-based “solutions” for lifesaving tasks.

The Bluetooth protocol is inherently an unreliable near-field protocol, used for mouse, keyboard, and data transfer, but it has never been designed for monitoring 24×7 as it is too susceptible for external disturbances, and might fail to reconnect automatically when the link has been broken.

The hardware which promises to get you back to the point where the connection has been lost relies on two pieces – one is the GPS chip, which is nothing more as a game console implementation in most devices, and may put you easily off by quite a distance, most of that when the device is below deck (where it will most certainly be) so the sat sights are not totally perfect.
The other is the compass chip which usually deflects up to 25° unless permanently recalibrated by moving your mobile through the air describing huge figures of an eight. I doubt you did this by chance just a couple of minutes before your MOB, neither you will think of that when you get the alarm.

And, to Andy, the mobile MOB solution lulls you into a false safety feeling “they can find me in case” – no, they won’t. If they are lucky they will get back to the point where you fell in – my bet that you’re no more there when they arrive. In no way would it have them “think more seaman-like”. If they don’t spring for an AIS beacon on Chesapeake it would be better to have no beacon at all and remembering that on the other side of the fence is Johns 100ft cliff waiting. THIS would be more seaman like.

It is the same as Johns MOB prevention book states: wrong installations are dangerous alone by making you believe you are safe, when in reality you are not.

(Disclaimer: I have my mobile on board, and I do have the Navionics app which I use for rough pre-planning as well as the GPS-based anchor watch. Alas, the latter had me jump out of the bed more than once just for a false alarm. But only in this case I believe its “better than nothing”)

Philip Wilkie

Cripes; I didn’t even imagine someone would attempt a POB solution using Bluetooth. Without even reading all of John’s no doubt excellent analysis the answer must be obvious; the words ‘safety’ and ‘Bluetooth’ simply don’t belong in the same sentence.

A similar parallel exists with PLB’s and EPIRB’s; while there are lower cost solutions like SPOT that can be useful in some scenario’s … when it comes to an emergency nothing but nothing substitutes for the real thing.

Philip Wilkie

My gold standard here are industrial safety protocols like CIP Safety. The four core components that ideally should be present in this kind of application are:

1. A hardware layer that is both robust electrically, with known MTTBF’s AND detects hidden faults. In other words no fault can occur that will only become apparent on demand.

2. A communication protocol that embeds multiple layers of error checking, sequential packet numbering, encrypted station ID’s and rock-solid reconnection methods.

3. Application layer code that is written using pre-defined functions (library modules) that have been fully tested by an independent authority to a specified and understood Safety Integrity Level (SIL).

4. And finally a mechanism to lock down access to ensure only intentional and authorised changes can be made to the code and hardware.

A POB app running on a smartphone using BT as the carrier fails to tick any of these boxes miserably.

Colin Speedie

Hi John
as someone who struggles with text messaging it’s probably true that I should not be allowed anywhere near any apps, no matter how effective they may be. But running a boat before all of this stuff appeared tended to focus the mind on what we would do in the event of such an emergency and I can confirm that it wouldn’t have been an app, even if such things had existed then.
I’m in total agreement with your focus on staying aboard – the best thing that can be done. If the worst should happen, though, then simplicity and speed are what matter, and that is what we focussed on. We viewed everything that used valuable time thinking and not acting to be avoided at all costs.
Not to say that the MOB button on the GPS doesn’t have a place and that these latest generation AIS beacons aren’t welcome – they are, not least because they are autonomous. I can see the benefit of that and it does appear that they work and don’t involve distracting the crew at such a critical time when clear thinking and action are the best hope for a successful outcome.
Best wishes


Hi Colin,
Most people who know me would characterize me as a radical– hopefully in the good sense of the term. “Radical— to go to the root of the situation. ”

In that spirit I would state absolutely that the smartphone is the worst and most addictive drug that has ever been invented. In terms of its impact upon human consciousness and loss of active interaction with other people and the natural world, crack and heroin are mere chocolate candy. App designers are nothing more than street corner dealers of the addictive drug that Steve Jobs unleashed upon the world. Psychiatrists are just starting to notice clinical impacts upon the mental development of young children, but walking through any airport lobby and observing the phone zombies that populate it should be sufficient to alert one to the fact that something is seriously wrong.

So should sailors rely upon their smart phone in MOB situations? Hell no! Throw the damn thing overboard! Free the mind and concentrate upon staying on board! Take your Apple or Galaxy to the nearest skeet range and use it to save a clay pigeon.

Nothing in my rant denies the fact that the smart phone is a handy tool, especially on board a sailboat! But when the strength of the signal becomes the dominant factor in selecting a cruising destination its long past time to choose freedom over addiction.

Charles L Starke

Dear John,
I agree 100% about smartphone addiction! How come I love reading all these comments on my phone, and I’m planning on a cell phone booster on my boat? Ha!
I agree 100% on your position on an AIS MOB Alarm and not relying on a smartphone alarm. I can’t even get a smartphone anchor alarm to be reliable even when fed information with a good GPS.
Best wishes
s/v Dawnpiper


I’ve Seen the Needle and the Damage Done— Neil Young

Addicts always believe that addiction is something that only happens to other people!


Hi John,
For me at least, a passage just starts being good on about the third day. And that is because it takes about that amount of time to become mentally disconnected from the land world and tuned into the pace of the wind and waves and sun and stars. That state can even be enhanced by receiving and analyzing digital weather information to enable a larger vision, but it can’t survive replicating smart phone addiction on a sat phone.


One issue that needs to be resolved with the AIS beacon is the battery. Mine somehow triggered inside closed life jacket and went unnoticed, running down the battery. I was told that battery needed to be replaced by a service center in Seattle and I am in Mexico. For some reason the battery is made up of two lithium batterys taped together with a little wiring harness so will be difficult to make a new battery myself. I just discovered this so maybe an easier solution is out there. Still would not bother with the phone based system for all of the previously mentioned reasons. Following John’s recommendations for jack line placment is my primary solution.


John, looking at what happened with the mobile industry I honestly doubt your wish might become reality. I still remember the “good ol’ times” when we just had to open the back of the mobile and remove the battery to plug in an exchange module – this has all vanished to “make things smaller”, I believe to make things more expensive, rather.


The ideal functionality would be the combination of the newish tiny little wearable/pocketable 406 EPIRB PLBs and an AIS beacon. The 406 PLBs have a shorter-range tracking frequency built in, but almost no cruising boats have the means to track it. Now that AIS exists it would make more sense to drop that tracking frequency and have the 406 EPIRB PLB also transmit an AIS signal. So you would have both long-distance emergency location and short-distance homing capability for POB retrieval. A boat that sails outside the 20-mile tracking range of the target would be able to call any international SAR center using SSB, Ham, or satphone, and get the coordinates picked up by the 406 EPIRB network, then route towards the coordinates until the AIS signal appears for close-range homing.

I’m sure this is coming, but wonder why it is taking so long given that both technologies have existed for a while now. It may be that the regulatory requirements for 406 PLBs require the old tracking signal.


Stein Varjord

Hi David.
With any type of emergency item, I think it might be useful to think about useful rescue scenarios. Who will be able to do a useful effort. If a whole boat goes, a proper EPIRP notifying everybody anywhere is obviously the only option. Meaning satellite and all else available. Hopefully, the survivors are not swimming but in a state where they can tolerate several days of waiting for help.

In a POB situation, that’s entirely different. The one lost has a window of survival that is normally not more than a few hours, (more on that below). In colder waters, even 10 minutes means certain death. That means that, with an overwhelming probability, the only useful source of help is the boat he/she fell from. Other sources of help are always nice to get, but this will rarely be of use.

This means any means to make it easier to be found by that boat or in a lucky case, some other boat nearby. In the old days that would mean a light, a whistle, or a flag on a high pole. They are still good to have, but rescue is far from certain… An AIS beacon can, if it works, be a way better help than all of those combined. Satellite can’t really contribute, mostly. Maybe the proper authorities can do a lot and direct many others to the spot, but they will rarely come soon enough, even in high traffic areas.

My conclusion is that if the satellite option doesn’t have any detrimental effect on price and performance of the AIS functions, fine, I’ll take it, for the very few occasions when that is helpful. But in reality, it costs quite a lot more, and the battery will be much larger or last a lot shorter. This makes a combined unit perform less well and less safe than a pure AIS unit. I wish to be found by those very close. I don’t care if the shore based people know where my corpse can be found. Thus: AIS only on that beacon seems smart….?


Agree with your comments above, except one thing. The 406 PLB beacon already transmits a homing signal (126mhz?) along with the 406mhz EPIRB signal, using both battery power and circuitry. I think the 2nd signal would be more helpful if it were an AIS signal. I’m assuming the boat will have its own larger 406 EPIRB. One of the biggest fears as a cruising couple is that we’ll wake up from an off watch and our partner or other crew is gone. It would have to be because they broke rules about being clipped in, not leaving the cockpit without waking the off watch, etc, but that’s the fear, and those things happen. Agreed that a POB’s best help is the boat they fell off of. Those little 406 PLBs they sell would be better if they transmitted an AIS signal instead of the old-school homing signal that no cruiser can track. Even if all those points of failure for the AIS alarm failed, assuming the POB was able to fire up the beacon, in warm-enough water to survive some hours (where a lot of long-distance cruising is done), you’d be able to go back and find them.

Stein Varjord

Hi John.
That’s an interesting text and video. Looked up a bit more too. He’s called Dr Popsicle. 🙂 His analysis makes logical sense and he thoroughly demonstrates it. Interesting to learn that we can survive and function that long, but that also fits my own observations.

As a kid we used to wade in a specific favorite small river delta for hours when on mountain trips. Memurubu at the Gjende lake, Norway. It was fascinating with sandy bottom, lots of small canals to explore and games to invent. The water was mostly 20 to 50 cm deep and around 4 degrees C, as it came straight from a glacier. It was very cold in the beginning, but getting in gradually, one got used to it. The air was maybe 20 degrees plus sun heat, so we didn’t get cold from this. Our legs had almost no feeling, and maybe it wasn’t healthy, but I’ve not had any troubles from it…. I’m 57 now.

The body can reroute the blood away from the surface and some body parts to keep the core temp better. I assume that also has a bigger effect when immersed than I thought. Also it matters a lot how much and what type of clothes we wear. The professor mostly wears a lot of clothes, as a skier falling through the ice would. I’ve tried it in sea water with normal indoors clothes. Jeans, t-shirt and shirt. This was a mandatory part of a safety course needed for being certified for offshore racing.

We had to jump from 3 meters into the sea in Oslo in late January. This was to simulate evacuation of a ship. The water was minus 1 C at 50cm depth…. Salty and constantly forming ice on top. We learned the necessity of holding our mouth and nose squeezed closed with one hand to avoid immediate drowning from the immersion gasp. We also learned that we had less than 1 minute to get into the life raft. If we used more time, the arms would be too weak. We didn’t seriously test delaying it though…. It’s really painful to be in water below the freezing point. Especially in the beginning. The doctor makes me think we may have quite a bit more time, but hurrying is still smart, I think. 🙂

We also learned about how to deal with hypothermia, which is quite tricky and quite relevant with the POB topic: Getting into a warm shower or getting other large amounts of external heating is very dangerous. It starts circulation of the blood in the arms and legs before the blood has been heated. When that cold blood reaches the body core or the brain, a sudden death is very probable.

The heat has to come mostly from inside of the cold persons own body. Insulating and slowly heating the head, neck and torso, mainly above the waist, in that priority. Let it take time. Keep arms and legs out of contact with the torso, insulated is ok but no extra heat. Warm beverages are good, if the person is fully conscious. People can survive very low body temp. Even long after passing out, they can be saved. The majority of deaths after being saved is reportedly due to wrong reheating. I think too few people are aware of this, even among long distance sailors.


Having worked in the mobile tech industry using both bluetooth and mobile phones, I wouldn’t touch either with a bargepole in matters of safety. Bluetooth is demonstrably unreliable.

By the way, bluetooth is a fairly power hungry protocol so will potentially kill the beacon quickly. I therefore wouldn’t contemplate it for battery monitoring puposes either! Ditto wifi.


Interesting article, but a little biased in my opinion. As others have said in the comments, I think it’s very unfair to make this a comparison. Those two products complement each other.

First, the smartphone bluetooth option is way cheaper than you said, provided you already have the smartphone of course. Any bluetooth device will work, and basic bluetooth fitbit clones sell under $20 on Amazon. And there are a lot of free apps which will sound an alarm if a bluetooth connection is lost for more than a certain time (say five minutes to mitigate false positives).

For $20, I can’t see how any sane person might choose not to use an extra alarm which might or might not work, but which might one day save a life. Granted, five minutes is a very long time and finding the MOB will be all but impossible in a pacific storm, but if day-cruising in a coastal area, this alarm will eventually sound and the coastgards will have a very high chance of rescuing the MOB … it’s arguably way better than nothing.

The AIS PLB isn’t perfect either. I agree that if the alarm sounds, homing on the MOB will be very easy, but that’s a big if ! The technology relies on a string of single points of failure. The PLB can fail to power up (eg a battery problem), it can fail to emit (eg the antenna is underwater), the boat can fail to receive the signal (any problem with the VHF antenna or the splitter if there’s one installed – my Vesper Marine splitter defaults to VHF traffic and ignore AIS traffic in case it fails), and lastly the AIS alarm unit itself can for some unknown reason malfunction. Granted each step is probably quite reliable, but there are a lot of them ! Actually, I once lost all AIS data on my RayMarine plotter, and had to reboot to get it back ! The smartphone thing is just a single item that can fail : the smartphone (and arguably the app)

There’s no question that it makes a lot of sense to buy an AIS PLB (or rather one per permanent crew member), but I think there’s a strong case for investing $20 in a bluetooth alarm as well … just in case the first line of defense (not falling overboard in the first place) and the second (the AIS PLB) both fail


Hi Brann,
sorry to chime in here, but isn’t it biased as well mentioning a “big if” for AIS reliability and advocate the use of a Bluetooth homing device in the same sentence? The mobile solution has the far bigger “if”. Actually it is not even close to comparing apples with oranges here, you are simply comparing devices that have never been meant for, nor engineered for safety issues.


Fair point. The “If” might not be a “big if” but it is still an if, and again I’m not advocating using bluetooth instead, but in complement. Also, the possibility that a bluetooth device fails to stop transmitting while overboard is zero, whereas it’s clearly possible that an AIS PLB might fail to start transmitting. If you add the Splitter and the AIS Mob Alarm, imagining the whole chain *might* fail seams reasonable, don’t you think? My AIS splitter certainly considered this possibility, as they actually made sure to provide a fail-safe VHF-only in case of failure

Even if the probability something doesn’t work as expected is only 1%, isn’t it better to have a cheap $20 bluetooth fallback, which will certainly raise the alarm, even if it doesn’t allow you to track the MOB properly ?

I said 1% for the sake of argument, but honestly, in my opinion this is a conservative estimate. I saw a test in a french magazine (Voiles & Voiliers) a few months ago which clearly stated that quite a few of the products they tested failed to behave as expected.

And again, I am *not* advocating not using AIS PLB, if I had to choose between bluetooth and AIS I would go for the latter. But nobody forces me to make such a choice!

I’m just saying no technology is 100% bullet-proof (actually, I’m quite surprised to hear John on the other side of this argument !), and that if it fails, a cheap 20$ bluetooth thing could really well save a life.

This really sounds to me like common sense, and I’m beginning to question my sanity …


While I internally debate if my 2 cents added to this conversation would have any productive value, I wanted to add a quick note.
During the clipper race, 1/2 AIS POB beacons did not work as intended. The AIS beacon on the MOB pole was never received (they used the personal AIS to locate victim). The report speculated that it was perhaps because the wind was so high, the MOB pole was horizontal and the unit was too close to the water, but again speculation. It could have been damaged upon impact/entry, entangled in other gear, faulty, ect… My only takeaway is that these units are not 100% reliable (what is??) either. Perhaps redundancy is good is overboard systems.

Eric Klem

Hi John,

I had not looked into the cell phone based MOB apps and had not realized that they use bluetooth, thanks for the heads up. When buying my current cell phone, I picked the only available one that meets MIL specs but still don’t ever use it for anything mission critical whether it be on the water or off.

One thing that I learned early in my career and always try to keep in mind is that it is usually a bad idea to do a belt and suspenders approach unless both the belt and the suspenders will do the job on their own. In design, people often try to put feel good backups in but unless these are given the same design rigour as the primary system, they usually just amount to a distraction that actually lowers overall reliability as when the primary system fails, they do too. In sailing, it is so easy to buy tons of gear thinking that it will improve safety but in actuality will reduce time and money resources that could be better spent. To me, one of the most important decisions is how much of this stuff we feel we should have and I tend to come down on the side of simplicity when compared to what I see as the norm. Never having used one, I do like the concept of AIS based devices even though they do add complexity.



Thanks for the thoughts. I was looking at getting two of these, but after reading all of this, I won’t. I wondered how it would work on Bluetooth for distance, and was taken in by the adds of it giving a direction and finding someone. I thought they’d be good on the river where I normally sail. And I almost always singlehand as it is, but thought, for the few times someone is with me, it might be good. But I see it isn’t.
I don’t have AIS as I’m inshore most of the time, but do have DSC. Aside from a few cry like a third grader crossing the fun Columbia River bar.
On a side note, I was on the development team for bluetooth. I did the testing and validation. Put it through a lot, but only across the lab. Someone said above that it was developed to replace a meter long wire. In reality when we developed it, we had no use for it. Went on the shelf for possible future use. We all thought it was funny. We never dreamed people would be addicted to walking around talking. But hey, lots of royalties when it gets used now. (Not for me though)


The joke to us was a simple, slow, low power solid state transceiver that couldn’t talk it’s way out of a paper bag. And coming from the high end talk anywhere at anytime communications world (read Govt) it didn’t make much sense.
It’s great for what it does, but this POB thing seems like technology for the sake of technology. Doesn’t do much, but it’s the latest thing that makes little difference. (Sorry, a peeve. So my boat is simple)
It really is a simple device. It’s the technology at either end that makes it seem so cool. But in reality WIFI isn’t much different.
Don’t know how it got it’s name, but the company wasn’t that good at marketing. A bit arrogant and ignorant on how the world thinks in that area. Brilliant people though, in their own world, but that wasn’t enough to save them in the end.
I worked on a cutting edge device to control everything in your house and bring you the internet, or anything you stored, from a tablet. Years before its time. It was a HOme Technology Management system. Never took off. Why? For one reason, they called it HOTMAN. No joke. So where Bluetooth came from I can only guess.


A thing on smartphone apps. So I get an advertisement for Sailgrib AA, an anchor drag alarm that works off your phone. Cool. So I tried it on the dog, worked good, down to about 2 yards. Worked fine, once, in real life too. Then I anchored at the end of a runway of a busy airport. Fun to watch the planes at night.
It lost itself and reset six times in four hours. RADAR interference? Who knows. I use my MFD alarm and it worked fine several times. But, lulled into the better than nothing app? Current there is around 3 knots, a line of dolphins, pilings for erosion, a hundred yards down. Anchor goes at night? Not cool.


Good points. It was below.
Thanks for your insight to things. It’s refreshing.

Dick Stevenson

Hi John and all,
Thank you for poking holes in the advertising hype that we are all subject to. Weems and Path (and all the others) should be ashamed of themselves and the commercial maritime media should be as well.
I must admit that I did not read every comment carefully as I was already convinced that if I am unable to use Bluetooth consistently successfully in my everyday life (and I cannot) then no safety device will be dependent on it. The following is about setting up the MOB1, which, we found not to be an easy or straightforward task, so if I missed someone else doing so, my apologies.
In a major upgrade of our safety systems last year, we bought Spinlock vests and the MOB1. On a purely pragmatic basis, I would, at the sales end where they are still invested in making you happy, have them help you set it up. We bought ours and, living aboard and on the hook, we had limited internet etc. and had a real challenge figuring out how to get the device configured. I am not on board now where my notes are, but, from memory, I remember one instruction had us hold the device to our computer screen for programming (or something like that) and, after multiple attempts, we could never make that work. After much frustration and calls to the manufacturer, we discovered the laptop needed to be plugged in to get the screen brightness to the level necessary to program the unit. The instructions never mentioned that as an issue and we never considered it. There were a few other areas of complication where we met dead ends till we finally got things sorted. It took much longer than needed and there were times, had we not back-tracked, where we might have thought the unit configured properly where it was not: a potentially dangerous situation. We find it quite fussy, but, perhaps, that is somewhat unavoidable in a complex device.
All this would have been much easier at the sales end if there is someone who has been down this particular road and has good internet to walk you through it.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi John,
Thanks for the reassurance that it would have worked regardless of the success configuring. I “knew” that but I always worry that if every i is not dotted and t crossed that electronics will confound me. Dick

Charles L Starke

Dear John & Dick
The MOB1 AIS unit may be programmed with two MMSI numbers. The first is designed to call own ship. The second allows a group call MMSI to be programmed only in the US, according to current regulations. But unfortunately, current regulations don’t allow an MOB1 to call this second MMSI VHF alarm until 1/2 hour after a person in the water incident. I am not sure if a foreign vessel can pretend to be US to allow a second DSC programming and VHF call. The MOB1 programming program initially asks if the vessel is US. I also found, like Dick, that a portable computer screen would only allow MOB1 programming if the computer had an external power connected.
The usefulness of this DSC MOB1 calling arrangement is that a race like a Bermuda, Transpac, Volvo or Transatlantic, may choose a group MMSI just for their race. Then any nearby boat in the race will also get a DSC alarm on VHF and an AIS position on a plotter or AIS screen. This might speed up any coordinated man overboard retreaval attempt.
Current Coast Guard regulations allow for easily generating a legal group MMSI by adding a “zero” in front and putting a zero” at the end of any legal FCC MMSI.
I would think that a change in current regulations to allow an immediate group DSC VHF call to go out, and to allow non-US boats to program an MOB1 with a second MMSI are in order.
Best wishes,
Charles L Starke MD FACP
s/v Dawnpiper


I seem to remember having read the name Bluetooth is taken from Harald I. Gormson called “Harald Blåtand”, king of Denmark from ca. 936/958 to 987 and king of Norway from 970 to 987. Don’t know why or how the Bluetooth developers elected to name it after an old king.

Early last Summer, before our 3-month trip around the Baltic, I ran jacklines around the sprayhood on both sides to the mast, from the mast to the foredeck, and also in a loose loop around the cockpit table. Each of the 4 jacklines has a dedicated tether attached to it with a Kong Tango and a Wichard Snapshackle on the person end. All as it says in John’s book – and it all seems to work very well on our boat. The foredeck jackline terminates in a deck eye in the center of the foredeck, not where the forestay is attached. That way it would be hard to get over the lifeline or between deck and lifelines even in this problematic area. The cockpit has a big folding table in the center, they way mass produced french boats have. I ran a loop of jackline webbing around its two posts, into which the tether is clipped. This allows to move all the way around the table, sit behind the wheels, even to do loops around the table, but will not let me get even close to the lifelines. It works so well that I had to unclip when the time came for me to throw up one dark night going upwind in 25 true. When going below, the cockpit tether can be left dangling down the companionway, ready to be clipped in again while standing on the lower companionway step.
I also got comfortable harnesses for everyone with a solid and quick lock. These we finally wore permanently at night or in bad weather, unlike the several sets of lifevests, which were just too uncomfortable to wear permanently. When wearing a foul weather jacket, you have to wear the lifevest over it, so both lifevest and jacket have to come off every time when going below and be put on again a minute later. The harness can be worn under the jacket safely, either with partially open zip or with the tether exiting under the jacket.
Our daughter would rather stay below than put on the lifevest, even though it is an expensive automatic one, just the right size for her. With her own harness and tether, she came up much more often to look around.
I used bowline knots in all the webbing, because it is much quicker and has no problems with UV deterioration of the seams (the tip I picked up here in the comments). The whole setup took two half days to make.

The point being that this relative small and not expensive and quick to do change to the boat, and the change in our habits that it allowed, in my opinion, improved our safety much more than even the best electronic device could ever have.

I have used a Standard Horizon GX2000 (the model with an AIS interface, not a dedicated receiver) for many years and am generally happy. I selected it for the ability to pick MMSI numbers to call from a list on the radio rather than having to copy the number from the AIS display. It turns out I have never used this function in earnest as normal calls via DSC are still very uncommon. If DSC-initiated calls were routine, I would probably be unhappy with this radio as the list of AIS targets the radio shows is only 10 entries long (the closest targets; the other possibly hundreds of targets are simply truncated; you can’t scroll down the list).
I might consider personal AIS beacons, but not this winter, and if I do, I might get these instead of the MOB1:
They are programmed via, don’t laugh, Bluetooth…
If I make that change, I might also change to the SH radio with dedicated receiver as I can then just leave the radio on at anchor, which uses little power, without having to run the AIS transponder 24/7. I would first make sure that it alarms on AIS SART beacons, though. Or maybe Icom has a similar model?

Raymond F Smith

I am entirely with you on this one, John. I was intrigued when I saw the Pittman award, but I did some calculations (as in your article) about how quickly I could get the boat turned around and realized there was no way I could do it within bluetooth range. Also, I have found bluetooth to be an unreliable technology in other applications. This is just a bad idea.


I’ve stayed out of this one for the most part. Frankly, I think this wasn’t a fair comparison in the first place, and John KNEW this would spark a debate.

I am a bit shocked at how the majority are so quick to dismiss this as new, unreliable technology, AND how some of the stories shared feel a bit luddite-y to me. It’s not always technology’s fault if you don’t understand how to use it in the first place. I agree that offshore it’s not an applicable tracking device, but then it wasn’t meant to be. But, it is funny how quick everyone is to adopt the AIS version as the gold standard, when not too long ago that itself was questioned in much the same way. Likewise with GPS. And so on.

Maybe the debate should be about marketing & media, rather than the product itself?

And look – we’re spending all this time fussing over an MOB technology that addresses a problem AFTER the person has gone over the side – let’s leave this on here and get back to thinking about how to stay on the boat in the first place.

Why aren’t we talking about fitness, for example? Or the loss of balance as people age? To me – and this comes with the experience of sailing with 50+ people per year, of all ages and fitness levels – the SINGLE BEST WAY to stay on the boat is to be fit & agile. All the rest of the safety equipment – PFDs, jackline setup, cockpit reefing, etc etc – are all ways to simply mitigate the problem of not being physically fit enough in the first place.

Where’s the featured article and the 80 comments on that?


Sorry Andy. You are completely right and on-point with your remarks on fitness and staying on board as the main concern. But this article is just about this specific MOB tracking solution, so your post reminds on a kind of whataboutism that a knowledgeable person as you are should not need to use.
You’re correct that AIS as well is not a 100% secure safety solution – basically there is nothing that’s 100% in boating, IMHO. But from my point of view, being envolved in the telco/mobile business I simply _know_ about the limitations of the BT technology, and others have pointed that out much better than I did.
For me I hope I will never ever be required to use an MOB homing solution so my main focus will always be that the crew stays on board, that’s for sure. But when the worst should happen I want to rely on technology that has been tailored to the specific task.


Fair enough. I’m just trying to change the narrative and move on – we all agree the smartphone solution isn’t the best solution for the task. How many ways do we need to say it? John said it well enough in the article too. I’m not arguing with that at all.


Hi All,

Formal apology here for my comment above – I’m sorry for going out of bounds, and did not intend to offend anyone. I get passionate about all of this stuff. This one was personal for me because of my relationship with Weems & Plath, and puts me in an awkward position as both a user of their products, a beta tester of the Crewwatcher itself, AND an advocate of offshore safety in general, so I was on the defensive from the start and let that influence my commentary. That said, it’s no excuse, it was out-of-bounds and doesn’t belong on the forum.

I DID, however, test the smartphone beacons for a year on Isbjorn, so did get some valuable insight into how they work – I only had prototypes, so I won’t offer any conclusions here, but we do have a set of 6 production units onboard – in addition to the MOB1 AIS beacons – so after some real-world use with the production units this coming summer, perhaps it’ll be worthwhile offering some feedback.


Marc Dacey

Andy, other than being fit and in your 30s (and strongly motivated to remain so, I would imagine, given your day job), do you have a particular “voyaging-oriented fitness regime” you follow to maintain that fitness? Because while you need a certain amount of strength to work a boat, agility and balance are different, if allied, skills, and I would imagine they are gained and maintained differently. Perhaps a future article here? A lot of us could use the tips, I’m sure…and it may keep us from ever tripping that AIS beacon.


Yeah I think future article is they key here, so stand by for that. But, you’re right – balance and agility are a different kind of fitness and can be trained differently. NFL lineman and BIG men, but they are some of the most agile guys on the team. Perfect example there.

Marc Dacey

My martial arts training has kept me on more than one deck, so I concur. I look forward to that article in one of your many venues.

Rob Gill

Hi everyone,
Interesting thread and wow, lots of comments. I am interested because for our recently completed SW Pacific circuit we did not take personal AIS beacons. I would be interested in your thoughts, but here is ours:

1) We would have between two and four crew for each hop with family and friends joining at different times, even though much of the voyage was Jenny and I alone
2) Family and friends new to the boat were the most likely to go overboard
3) We wanted one MOB procedure, no matter who was lost overboard
4) We just couldn’t justify four beacons, given this could have been a one-off ocean voyage (most of our cruising is coastal NZ) and this was our first ocean passage on Bonnie Lass
5) I didn’t want crew safety in any way to rely on tired crew remembering to hand-off a single “watch keeper’s” beacon, especially as all crew are mandated to be tethered in most conditions in the cockpit, and always at night, and no one was allowed on deck at any time without someone watching and being tethered.
6) We had set up the boat as per John’s “best practice” approach so that no one tethered in could physically go overboard, either in the cockpit or on deck
7) We analysed that the most likely time for a MOB was when crew were around and we were in an emergency or sail handling manoeuvre, and someone (most likely me) made an error.

What we did do:
1) We have a self-inflating Dan-buoy and ours has the integral self-inflating Jon-buoy life-ring, which activates in the same way as a lifejacket . We gave the supplier/service agent an AIS beacon to try, and after some trials and testing, our single AIS beacon was attached to the manual inflation tube where it auto-activates as the life-ring activates.
2) Our MOB process includes the immediate release of the Dan Buoy and has CLEAR instructions for the MOB to do everything they can to get to the DAN Buoy. If visual contact is lost with the MOB, that is where we would return to start our search. Obviously the key is rapid release of the beacon by a crew member and conditions that allow the MOB to get close to the Dan Buoy. Each crew had a light, whistle, reflecting tape and hood on the lifejacket.
Since that time we have returned and are already talking about our next adventure. And we will be considering four personal beacons then.


John, maybe you have stats on this somewhere, but one looming question that I just thought of here is this – how many shorthanded, OFFSHORE cruising folks actually go overboard? You referenced the Clipper Race incident earlier, and I know a handful of Clipper skippers, all who swear by the AIS beacons and have used them in anger, and successfully (though the only incidents that make it into the media are the unsuccessful ones, unfortunately, where the POB is dead by the time they find them). But Clipper are doing a much different kind of sailing, and with a large crew – if they do have a POB, they can much more easily manage the recovery – getting sails down, driving the boat, visually looking at the POB, and having a dedicated crew on the chartplotter tracking the beacon.

So two parts here – do shorthanded cruising sailors actually go overboard offshore, statistically? Or are we trying to solve a nonexistent problem? And furthermore, what would say a double-handed recovery of a POB WITH a beacon attached even look like?

Say Mia & I are offshore, just the two of us, and she goes over the side. She’s clipped in, but is getting dragged along the side of the boat, knows that I saw her go in, and pulls the rip cord to release the tether. It’s dark, big seas. I have to get the boat back to her by myself – she’s got the AIS beacon on, and it deploys successfully and is pinging on my chartplotter like it should be. I’ve got our waterproof iPad in the cockpit with me since we don’t have a fixed chartplotter at the helm…my point is, there is a LOT to keep track of here by myself – I can’t get the sails down without taking my eyes off of her AND the beacon pinging on the chartplotter, for example, and I KNOW I’ve got a limited range until that beacon disappears from the screen.

Just thinking out loud here (I’m actually at the STCW course this week in Cowes, so this kind of stuff is top of the mind), with this scenario in mind, assuming we did all the ‘right’ stuff to keep the person onboard in the first place, as a shorthanded crew I think I’d focus first on visual aids – dayglow stuff and lights. Spinlock makes that new light that goes inside the inflated PFD to make the whole thing glow – never tested it, but I love the idea. I feel like if I react quickly enough with the boat, I’m more likely to visually see something than have to, by myself, track the beacon. I’d still have the beacon of course, but it would be further down on my list, and I’d do everything possible to avoid having to rely on it. Thoughts?

I think it’s worth thinking through all this, or else the beacon itself isn’t much use.

Stein Varjord

Hi Andy
I think you concerns are essential points to be aware of. The topic here is being able to find a POB, but there’s not much point in that if we’re not able to get the boat moving back to that point, or if we’re not able to get the POB back onboard and just have to watch as the person dies. Both tasks are potentially very difficult. In realistic weather, none of them can be managed unless it’s been planned and practiced and systems are prepared. Even with all the equipment and all preparations done perfectly, there is a serious risk of failure.

This is the reason I keep nagging about the psychology of safety items. The only way to be sure we don’t die as a POB is to make sure we never become one. We use equipment to prevent falling and to help when it still happened, but the equipment makes us relax, usually in the wrong way. That applies to me too, even though I know about my “weakness”. I think it’s important to use good equipment if it’s used right. If the equipment isn’t capable of what we think it is, or we’re not capable of using it, I think it’s better to not have the equipment and be really afraid. If you’re aware of accute danger, you think and behave accordingly.

Stein Varjord

Hi John.
I think you do the right amount of reminding. Actually just doing it now and then will make us a bit more alert on asking ourselves “does this belong here, or somewhere else?” Self justice, maybe? Either way, “the proof is in the pudding.” Like this very active discussion works great, I think, even with some digressions and feelings, produces a lots of food for thought. In most other fora, this topic, and most others, would have become a dogfight, including calling each other names.

Marc Dacey

There’s such a wide variety of experience and (generally impressively) informed opinion here that I find the digressions quite as valuable as the initial discussions from which they branch. I can understand, however, the desire on the part of the moderator to avoid the dreaded “thread drift”, but it does illustrate how some of these considerations involve a sort of holistic appreciation of boat gear and sailorly behaviour, and how attitude toward onboard risk management strongly influence gear preferences.

And I had no idea a topic like this would get 20-25 fresh comments per day!