COLREGs Explained, in Plain English

10 min read · Audio Fastlane

The COLREGs — the International Regulations for Preventing Collisions at Sea — are the rules of the road for everyone afloat. They have been adopted by more than 150 states covering the vast majority of the world's shipping, and for any watchkeeper they are simply not optional. Here is the plain-English version.

Give-way and stand-on: the core idea

Almost every encounter comes down to two roles. The give-way vessel is the one required to take early, obvious action to keep clear. The stand-on vessel is the one that holds its course and speed so the other can predict what it will do — until it becomes clear the give-way vessel is not acting, at which point the stand-on vessel must also act to avoid collision. Knowing which one you are is the whole game.

The pecking order

When two vessels could collide, the rules set out who keeps clear of whom. Loosely, the less manoeuvrable a vessel is, the more right of way it has:

So a power-driven vessel gives way to almost everyone, while a vessel not under command or restricted in its ability to manoeuvre is near the top. Remember that some definitions overlap — a vessel constrained by its draught, or one towing, is also a power-driven vessel — which is exactly the kind of detail an examiner will probe.

The key rules worth knowing by name

• Rule 5 — Lookout. Keep a proper lookout by sight and hearing at all times. It is the most broken rule and the root cause of most collisions.
• Rule 6 — Safe speed. Go at a speed that lets you stop or take effective action in the conditions and visibility.
• Rule 7 — Risk of collision. If in doubt, assume risk exists. A steady compass bearing with decreasing range means you are on a collision course.
• Rule 8 — Action to avoid collision. Make it early, make it obvious, and make it big enough to be seen clearly by the other vessel.
• Rule 13 — Overtaking. The overtaking vessel always keeps clear, no matter what type it is.
• Rule 14 — Head-on. Two power-driven vessels meeting head-on both alter to starboard and pass port-to-port.
• Rule 15 — Crossing. When two power-driven vessels cross, the one with the other on its own starboard side gives way.
• Rule 18 — Responsibilities between vessels. This is the pecking order written down.

Lights and shapes

At night, a vessel tells you what it is and what it is doing through its lights; by day, through shapes. Learning them feels daunting until you group them and lean on a few mnemonics. These rhymes are worth their weight in gold on a dark watch:

By day the same information comes from shapes: a ball means anchored, two cones point-to-point means fishing, a cylinder means constrained by draught, and so on. Master the lights and the day shapes follow naturally.

Sound signals

In clear visibility, short blasts tell other vessels what you are doing with your helm: one short blast for a turn to starboard, two for a turn to port, three for operating astern propulsion, and five or more short, rapid blasts as the danger signal — "I do not understand your intentions." In restricted visibility the pattern changes to long blasts on a timed cycle.

Why crew struggle — and what fixes it

People find the COLREGs hard for honest reasons: there are a lot of them, they involve visualising vessels moving in three dimensions, and most crew do not get to apply them often enough to keep them fresh. The fix is repetition in a format you will actually use. Hearing the rules read aloud, again and again, is one of the most effective ways to make them stick — which is why we recorded them.

Frequently asked questions