Every helmsman has had that moment : a ship's lights at 2 a.m., a closing bearing that won't move off the compass, and a sudden realisation that the COLREGs you skimmed before your exam are about to matter. The International Regulations for Preventing Collisions at Sea are not legal trivia. They are the common language that lets a Polish bulk carrier, a Breton trawler and a chartered 38-footer share a TSS lane without anyone radioing the coastguard. Knowing them in plain language, the way you'd explain them to a new crew on the wheel, is what separates a careful skipper from a lucky one.
Why the rules still matter in the age of AIS
Electronic plotters and AIS overlays have changed how we see traffic, but they haven't changed who is the give-way vessel. The COLREGs assume both skippers are looking out, judging risk by eye and compass, and acting early and clearly. Plotter targets help, but a Class B transponder updates every 30 seconds at low speed, and small fishing boats often don't transmit at all. The rules exist precisely because radar and AIS are aids, not substitutes.
If you want a refresher on how to make AIS work for you rather than against you, our guide on reading and interpreting an AIS to avoid collisions goes into the practical side : CPA, TCPA, and the targets you should actually worry about.
The five rules that do most of the work
The COLREGs run to 41 rules and four annexes, but in day-to-day coastal sailing, five of them cover something like 90% of the situations you'll face.
- Rule 5, lookout. "By sight and hearing as well as by all available means." That means eyes out of the cockpit, not glued to the MFD. On a short-handed crew, this is the one rule most often broken.
- Rule 6, safe speed. Safe speed is not hull speed. It's the speed at which you can stop or alter course in time, given visibility, traffic density, sea state and your own manoeuvrability. In fog with 100 metres of visibility, six knots can be reckless.
- Rule 7, risk of collision. If the compass bearing of an approaching vessel does not appreciably change, risk of collision exists. Take a bearing, wait a minute, take another. If it's the same, you have a problem.
- Rule 8, action to avoid collision. Action must be early, substantial, and obvious to the other vessel. A 5-degree nudge at half a mile is neither. A 30-degree turn at two miles is.
- Rule 13 to 18, the give-way hierarchy. Overtaking gives way to everyone. Power gives way to sail (with exceptions). On opposing tacks, port gives way to starboard. On the same tack, windward gives way to leeward. Two power-driven vessels crossing : the one with the other on her starboard side gives way.
Memorise these as a block. Everything else is either a special case (narrow channels, TSS) or a clarification.
Give-way and stand-on : what each vessel actually does
One of the most misunderstood points : the stand-on vessel is not "the boat with right of way". She has obligations too.
The give-way vessel (Rule 16) must take early and substantial action to keep clear. She decides how : a course change, a speed change, or both. A bold alteration to starboard, made at a distance, is almost always the right answer.
The stand-on vessel (Rule 17) must maintain course and speed, so that the give-way vessel knows what to avoid. But she may take action when it becomes clear the other isn't keeping clear, and she must act when collision can no longer be avoided by the give-way vessel alone. In a crossing situation, she shall not turn to port. Ever.
This is where many recreational skippers get into trouble : they're the stand-on vessel, they see a closing freighter, they panic and turn. The freighter, who was about to alter, now has no idea what's happening. Hold your course until you've signalled, or until action is the only option left. Five short blasts on the horn is the international "I don't understand your intentions" signal, and you should use it without embarrassment.
Sail versus power : the rules people get wrong
"Sail has priority over power" is the most over-quoted half-truth in pleasure boating. The actual hierarchy in Rule 18 ranks vessels by manoeuvrability :
- Not under command
- Restricted in ability to manoeuvre
- Constrained by draught
- Engaged in fishing (with gear deployed)
- Sailing
- Power-driven
Each gives way to those above it. So yes, a sailing yacht is generally given way to by a power vessel, but a 200,000-ton container ship in a deep-water channel is constrained by her draught, and your obligation is to stay out of her way. A trawler hauling nets is fishing, and outranks you. A dredger showing two black balls and a diamond is restricted in manoeuvre, and outranks you.
And the moment you start your engine, even if your sails are still up, you are a power-driven vessel. Show the black cone forward (Rule 25), and behave accordingly.
Between two sailing vessels, Rule 12 applies :
- Different tacks : the one on port gives way to the one on starboard.
- Same tack : the windward vessel gives way to the leeward vessel.
- On port tack, if you can't tell which tack the other is on, assume she's on starboard and keep clear.
Restricted visibility, narrow channels and TSS
In fog (Rule 19), the concepts of "give-way" and "stand-on" disappear. Every vessel must proceed at safe speed, navigate carefully, and if she detects another by radar alone, take avoiding action in good time. Two specific don'ts : do not alter course to port for a vessel forward of the beam (except when overtaking), and do not turn towards a vessel abeam or abaft the beam.
In narrow channels (Rule 9), keep to the starboard side. Vessels under 20 metres, sailing vessels, and fishing vessels shall not impede the passage of a vessel which can safely navigate only within the channel. In plain words : if a ship can only go where the dredged water is, you get out of her way, regardless of your sail status.
Traffic Separation Schemes (Rule 10) work the same way. Cross at right angles to the flow, on a heading at right angles, not a track. If your COG is 90 degrees to the lane while a 2-knot cross-current bends your heading, that is fine and legal. The rule is about your heading, because that's what other vessels see on radar. Planning the crossing properly is part of an efficient shipping route, and it's worth doing on paper before you cast off.
Lights, shapes and sound signals : the bare minimum
You don't need to memorise every combination in Annex I, but you do need instant recognition for the common ones :
- Power-driven under way : masthead white, sidelights, sternlight. Over 50 m, a second masthead light higher and aft.
- Sailing under way : sidelights and sternlight. No masthead white.
- At anchor : all-round white forward, black ball by day.
- Fishing (trawling) : green over white all-round. Other fishing : red over white. By day, two cones apex-to-apex.
- Restricted in manoeuvre : red, white, red all-round. By day, ball-diamond-ball.
- Not under command : two red all-round. By day, two black balls.
For sound signals, the manoeuvring ones every skipper should know cold : one short blast "I am altering to starboard", two short "I am altering to port", three short "my engines are going astern", five or more short "I don't understand your intentions, or I doubt you are taking sufficient action". Use them. Silence is not politeness at sea, it is ambiguity.
When the rules fail, and what comes next
Rule 2, the "rule of good seamanship", is the one quoted in every collision tribunal. It says the rules do not exonerate any vessel from the consequences of neglect, or from any precaution which the ordinary practice of seamen may require. In other words : if following the rule literally would cause a collision, depart from it. Insurance and admiralty courts will judge you on what a competent seafarer would have done, not on whether you were technically stand-on.
If despite everything an impact happens, the priority shifts to damage control and crew safety. Our notes on dealing with a collision at sea and the procedure for water leaks on board are worth re-reading before you need them, not during. And for the most common errors that lead newer skippers into close-quarters situations in the first place, the catalogue of dangerous navigation mistakes is a useful mirror.
The COLREGs reward skippers who think out loud, act early, and leave a clear trail of intentions, both on the water and in the boat's log. The Oria Box records your tracks, headings and speeds continuously, which means that if a near-miss ever turns into a formal enquiry, you have an unambiguous record of what your vessel actually did, not what someone remembered. Worth knowing the next time a bearing refuses to change.
