The Offshore Voyaging Reference Site

Don’t Alter Course to Port

At the end of my recent single-handed mini-cruise in a borrowed Hinckley 41 named Sable, I was working my way down a long channel in thick fog when a sailboat appeared directly in front of me and then turned to port.

Luckily I had been tracking them on radar and was ready for eventualities by standing at the helm and slowing right down to just maintain steerage way with the bow pointed to the starboard side of the channel. But if I had still been going ahead at even four knots I would have almost certainly tee-boned them. As it was, when I saw they were turning to port, I reversed hard to increase the clearance.

The crew of said boat was inside a full buttoned-up cockpit enclosure—probably why they did not hear my two-minute horn blasts—and steaming fit to beat the band in thick fog in a channel.

Why they did not see Sable on radar we will never know; maybe they confused her with a channel marker buoy.

Be that as it may, there are some important lessons in this incident:

When in doubt, we should turn to starboard (COLREGS Rule 14-a and Rule 19-d-i), even if we need to make a 180-degree turn (or even more) to avoid a collision. And, when in fog, particularly in confined waters, slow the hell down or, if any doubt, take all way off (COLREGS Rule 8-e and Rule 19-e).

A boat doing the same sort of thing nearly nailed Colin and Louise on Pèlerin a few years back. Come on people, navigating in fog is not a video game. We all need to read, and regularly reread, the COLREGS and follow them, as well as keep a good lookout. And that last includes opening up cockpit enclosures in fog so we can see and hear properly.

Don’t get me wrong, I’m not saying I have never made a mistake in fog, I have, but this kind of close call is both egregious and unnecessary.


A reminder that we have already done fog navigation in five chapters, see Further Reading below, so it’s not a good use of anyone’s time to redo all of that in the comments to this article, which I wrote to make a specific point (outside the paywall) about the dangers of turning to port and the importance of slowing down.

Of course, if you have a useful comment to add to the two points raised in this article, we are all ears. The same applies to comments relevant to the five articles linked to below.

Further Reading

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Lawrence Clough

Also do not steer directly to navigational buoys in heavy fog, lest you find another boat arriving at the same place at the same time.

This is particularly true for buoys marking channel entrances leading from an area of open water.

Rather steer a comfortable distance to the side of the buoy and be highly alert as you approach it. I was almost run down by a west bound lobster boat off Outer Green Island in Casco Bay, and would have been if I had been steering directly towards the buoy.

Lee Corwin

Find if you have large screens (12” or better) the split screen setting to be helpful. Radar and AIS on one side with chart on the other. There’s no difficulties sorting out what’s what. Also find not using the AP wise. Don’t depend on your remote nor the ten degree button. Stand at the helm hand steer and be next to the engine controls. Think the AP produces many of the close quarters or limited visibility collisions. If your draft permits it run just outside the navigational markers. Colregs doesn’t stipulate you must run a channel except in a few instances. That way you stay out of the way of most commercial traffic and the majority of recreational operators who have never read the colregs. Finally as a mom and pop if the engine is on one of us goes forward or at least out of the cockpit. You hear much better.

Marek Nowicki

Radio contact on 16?….if on colission course according to radar/AIS.

Jamie Still

While not applicable in this situation, I do believe when using radar in restricted visibility and a vessel is on your starboard quarter, that would indeed be a turn to port. (Forgive me for being a bit pedantic…)

Ernest E Vogelsinger
Rob Gill

Hi John, Ernest,
I believe the author is considering an ocean going ship as “stand-on” vessel – underway in a channel, with a small power boat crossing the bows (give way vessel). The ship going to full astern (especially if she is fully laden) is unlikely to reduce the collision risk in time, and could swing the stern to port (if RHS) and the bow to starboard exacerbating the situation.
Give way rights and sound signals change dramatically, once vessels are in sight of each other. At close quarters there is little time for VHF communication which can all too easily become “scanty” information. Sound signals are unambiguous, especially 5 or more short ones! I believe that was to be the subject of a part three article, but I couldn’t find it in my brief scan.
br. Rob

Rob Gill

Hi John, this may be a translation issue. The article refers to “inland waters” and as a Kiwi and ex navigator on ships, I took this to infer a channel. In a North American context this could of course be on an inland sea/lake. No argumentation from me about your conclusions though. – spot on. Rob

Eric Klem

Hi John,

Unfortunately the point you make is too true.

I was wondering whether you have a rule or set of rules for when you pro-actively change heading based on a non-visual radar only target and when you wait for visual contact? I personally do not have a rule and it is something I struggle to convey when setting up standing orders.

I have a hypothesis that modern chartplotters allow many more people to be out in the fog and also give those people the ability to travel at unsafe speeds. While I like my chartplotter it certainly feels more crowded out there in the fog than 20 years ago.


Eric Klem

Hi John,

Thanks for the reply. We shoot for the same CPA offshore but also try not to pass that close in front of a big target if possible if we are in a crossing situation. My observation on confined waters is that most boats seem to use radar as early warning only and take action once they have visual but there are some exceptions. I strive to take action earlier but it is not always possible such as the scenario you mention where you don’t have a lot of maneuvering options and you have only recently picked up the target.

Being one of the slower vessels out there, I find it can be a real balancing act in higher traffic areas. If you take early action, you are forever steering around boats much faster and maneuverable than you and greatly increasing your exposure time. By the time you get a proper plot on that boat doing 15 knots in the fog (unsafe in itself), the course deviation required is enormous to have any real difference if you are only doing 5 knots. One of the key learnings for me was to figure out what a lobster boat looks like on radar, steering around them takes very different tactics than someone running a course and speed.



But Not Always to Port..

“When in doubt, … turn to starboard (COLREGS Rule 14-a and Rule 19-d-i), … to avoid a collision. And, when in fog, particularly in confined waters, slow the hell down or, if any doubt, take all way off (COLREGS Rule 8-e and Rule 19-e)”

Incident May 2016. In fog. Visibility 50-75 Yards. Boat Speed 3 knots. Radar, AIS, Fog Horn, etc all in use. At helm open cockpit monitoring Starboard side (shore side) while I and a buddy boat (he to port and monitoring port side) proceed up Puget Sound separation 25 yards and a bit astern. Suddenly 4 headlights appear coming at my Starboard beam, closing at a high rate of speed.

First thought was to turn to starboard, but that would assure collision head on taking out mast. Hard turn to port, advance full power, begin to see separation, hit air horn – 5 blasts – repeat. Boat looks to be just missing stern. 3 sec from collision boat veers towards me 1 sec to collision boat veers away. Strikes my Starboard stern glancing blow. Buddy boats says my boat bounced across water 10 feet.

Point is. Be alert. Access the situation and remember to take action to Avoid the Collision.

James Evans

A security call to the other vessel (if there is time) can help. The value of that was proved to me on a crossing of the English Channel under sail a few years ago, when we were on the blower to ships and fishing boats all night. I was surprised at just how accommodating the big ships were, in most cases changing course for us.

Chuck Batson

There is a standard for “early and substantial action” avoidance turns under radar, I believe it originated in the Journal of the Institute of Navigation. I’m unable to share my copy of it, but it looks something like this:


Westbrook Murphy

The Andre Doria turned to port in fog and crossed the Stockholm’s bow.