CrewWatcher Versus AIS POB Beacon—Speed of Alarm Claim

While I was busy tearing marine journalism a new one, I happened upon a claim made by the manufacturer of the CrewWatcher smartphone-based person overboard alarm, see the above screen shot.

This is, based on my testing, and checking with Ocean Signal, simply rubbish, at least for the MOB1 beacon (and I suspect most others), which sends the first signal (and sounds the alarm on the boat) 15 seconds after activation, regardless of whether or not it has acquired a GPS position.

I suspect that the Dutch magazine came to their incorrect conclusion because in test mode the MOB1 does indeed wait until it receives a GPS signal—generally around 1 minute in our testing—before it transmits an alarm.

Anyway, in my never humble opinion, the “20x faster than AIS” claim is just marketing hype (quote a worst case without verification) and CrewWatcher should be ashamed for using it. Come on guys, we are dealing with safety of life here.

What Really Matters

MINIMUM homing signal coverage area for an AIS POB Beacon compared against MAXIMUM area for a smartphone-based POB Beacon.

And even if this claim were true, putting weight on it is a classic example of using the wrong criteria to make a safety gear decision. As I explain in my original analysis of the CrewWatcher, fast notification is near-meaningless when evaluating a beacon with an absolute maximum tracking range of 200 feet.

What matters most in Person Overboard (POB) recovery is finding the person again once they are no longer within visual range, something that will happen in most scenarios in less than 30 seconds. And at that point the CrewWatcher is pretty much useless, at least in comparison to an AIS POB beacon with a range of between two and five miles.

And while I’m blowing holes in CrewWatcher’s marketing, they also make a huge thing about a test done by the Dutch Coast Guard while totally missing that said test highlights one of the greatest weaknesses of the CrewWatcher:

The first test was conducted at a speed of 6 knots with the test observer at the stern deck. Once the MOB occurred the CrewWatcher app alerted the cabin crew most notably not by the audio alarm (which was drowned out by the combined 2400BHP engines) but by the visual change in color from green to orange.

(Emphasis mine.)

This is a benefit? For crying out loud, what it actually shows is that a beeping and flashing phone is a totally inadequate way to warn the crew that someone has gone overboard—something I pointed out in my original article.

Think about this for just a moment:

  • What if the remaining crew are sleeping?
  • What if the engine is on?
  • What if someone closes the CrewWatcher app?
  • What if the phone shuts down due to low battery?
  • What if the phone is on deck and the remaining crew below?
  • What if the remaining crew is deaf as a post like me?
  • POB incidents tend to happen during noisy manoeuvres like tacking or jibing.

A Much Better Way

Contrast that with an AIS POB beacon-equipped boat that can easily be set up so that when a crew member goes overboard:

  • A specific alarm sounds that can’t be confused with something else and is loud enough to wake the dead.
  • An alarm sounds on the VHF radio, too.
  • An alarm sounds on the plotter and, within one minute, the POB’s position is plotted, and then updated in real-time.
  • An alarm sounds on any other AIS-equipped vessels within a two- to five-mile radius.

And this gear uses a proven robust commercial quality protocol (AIS), not a phone. Further, AIS reception equipment is powered by the vessel’s system, and is in constant use for navigation and communication, so that any failure will be quickly noticed.

Bottom line, the CrewWatcher marketing page just proves, at least to me, what I have long believed: marketing can be absolute rubbish but still be dangerously effective. Reminds me of the Marlboro Man.

Further Reading


Please read my original article (Further Reading) before commenting so we don’t end up covering old ground again.

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John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 18 years, as co-editor/publisher of AAC.

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