In short
The COLREGs apply to every vessel at sea, from a tanker to a tender. A yacht is no exception.
Rules 5, 6 and 7 run all the time: look-out, safe speed, risk of collision. Without them the rest are useless.
Under power, the vessel with the other on her starboard side gives way (Rule 15); vessels meeting head-on both alter to starboard (Rule 14).
The overtaking vessel always keeps clear (Rule 13), even a yacht under sail overhauling a ship.
The Rule 18 pecking order is overridden by overtaking, narrow channels and separation schemes; in restricted visibility (Rule 19) nobody is privileged.
Rule 2 outranks everything: if the letter of a rule leads to a collision, you depart from the rule.
What the COLREGs are
COLREGs is short for the International Regulations for Preventing Collisions at Sea, agreed in 1972 and amended since: forty-one rules in six parts, from general provisions to lights, shapes and sound signals.
There is no main road and no side road here, and the word "priority" never appears: there is a give-way vessel and a stand-on vessel, both carry duties, and neither may plough on regardless.
Three rules that hold the rest together
Rule 5. Look-out
Someone is always looking and listening — by sight, by hearing, by radar and AIS where fitted. A chartplotter keeps no watch. The point is not to spot a vessel but to work out in good time whether risk of collision exists.
Rule 6. Safe speed
Your speed must let you read the situation, alter course and stop if you have to. At night, in fog, off a marina entrance and in shoal water, slow down. Six knots in a narrow channel can already be too fast.
Rule 7. Risk of collision
Take a bearing on an approaching vessel. If the compass bearing does not appreciably change, you are heading for the same patch of water. Without instruments, use your own boat: note which shroud or stanchion she sits against, and if she stays put against your rigging, risk exists. The rule is explicit — if in doubt, assume it does.
With a ship or a tug the bearing may drift and still leave no room: they are long, and a towline runs far astern.
Rule 8: how to manoeuvre
Action is taken in ample time and large enough to be obvious: one decisive alteration, not a string of nibbles. Given sea room, altering course reads better from the other bridge than changing speed — they see your aspect, not your log. Watch the result until you are past and clear; if it is not working, slacken speed or stop.
Who gives way: four everyday situations
Rule 13. Overtaking
If you are overtaking, you keep out of the way. Which side you pass and whether you are under sail make no difference. Overtaking means coming up from more than 22.5 degrees abaft the other vessel's beam; at night the test is exact — her sternlight alone, neither sidelight.
In doubt whether this is overtaking or crossing, assume overtaking. And no later change of bearing turns an overtaking vessel into a crossing one: the duty lasts until she is finally past and clear.
Rule 14. Head-on
Two power-driven vessels on reciprocal or nearly reciprocal courses both alter to starboard and pass port to port. Nobody stands on; the duty falls on both. The night signature is both sidelights, red and green, masthead lights in line. In doubt, assume head-on.
Rule 15. Crossing
Two power-driven vessels crossing: the one with the other on her own starboard side keeps out of the way. At night that vessel shows her red sidelight — see red, give way.
The rule adds practical advice with the force of law: the give-way vessel shall, if circumstances admit, avoid crossing ahead. Alter to starboard and go under her stern rather than dash across her bow.
Rule 12. Sail against sail
Between two sailing vessels Rule 15 does not apply. Rule 12 does, and the tack decides:
1Different tacks — the vessel on the port tack keeps out of the way.
2Same tack — the windward vessel keeps clear of the leeward vessel.
3On port tack, seeing a vessel to windward and unable to tell her tack, you keep clear.
The windward side is the one opposite to that on which the mainsail is carried. The third case saves the day most often: at night another yacht's tack is unreadable, and the rule settles it in favour of caution.
Rules 16 and 17: both sides have duties
Rule 16 covers the give-way vessel: act early and substantially, so the other crew can see you have given way. A five-degree nudge reads on nothing, eye or radar.
Rule 17 covers the stand-on vessel: hold course and speed so that you are predictable to go round. Once it is apparent that the give-way vessel is doing nothing, you may manoeuvre yourself; once a collision cannot be avoided by her action alone, you must take whatever will best help. Under power when crossing, do not alter to port for a vessel on your port side — and her duty does not go away.
Rule 18: the pecking order
Where vessels of different kinds meet:
a power-driven vessel keeps out of the way of one not under command, one restricted in her ability to manoeuvre, one engaged in fishing, and a sailing vessel;
a sailing vessel keeps clear of the first three of those;
a vessel engaged in fishing shall, so far as possible, keep clear of the first two;
a vessel constrained by her draught (three all-round reds, or a cylinder) owes nothing to anyone: everyone else must avoid impeding her safe passage.
For a yacht the reading is simple: under sail almost everything under power keeps clear of you, apart from the cases above. But a yacht with the engine running is a power-driven vessel even with the canvas up, and then you give way.
Rule 9: narrow channels
In a narrow channel or fairway you keep to the outer limit on your starboard side, as near to it as is safe and practicable. A vessel under 20 metres and any sailing vessel must not impede one that can navigate safely only within the channel: sail carries no privilege here.
Nor may you cross the channel if that would impede her, and you should avoid anchoring in one. Overtaking that only works if the vessel ahead makes room is arranged by sound signal: two prolonged and one short for the starboard side, two prolonged and two short for the port side.
Rule 19: restricted visibility
In fog there is no give-way vessel and no stand-on vessel: Rules 11 to 18 apply to vessels in sight of one another, and fog is a different world. Everyone proceeds at a safe speed with the engine ready for immediate manoeuvre, sounds fog signals and shows lights.
Detect a vessel by radar alone with a close-quarters situation developing, and you act in ample time. When that action is a course alteration, avoid turning to port for a vessel forward of the beam other than one being overtaken, and avoid turning towards a vessel abeam or abaft it. Hear a fog signal apparently forward of your beam and you reduce to bare steerage way — and stop if you must.
What outranks what
The order of precedence is not obvious from the text, and it matters:
1Rule 2 — responsibility. "I had right of way" has never excused a collision, and if departing from a rule is the only way out of immediate danger, you depart from it.
2Rule 19 — in restricted visibility nobody is privileged.
3Rule 13 — overtaking beats the Rule 18 order: a yacht overhauling a trawler keeps clear.
4Rules 9 and 10 — narrow channels and separation schemes beat it too.
5Rule 18, then Rules 12 to 15 — vessel types, then how equals pass one another.
Rule 18 opens "except where Rules 9, 10 and 13 otherwise require": the precedence is written into the text.
Common questions
Who gives way, a sailing yacht or a motor boat?
Under Rule 18 a power-driven vessel keeps clear of a sailing vessel — but only other things being equal. Overtaking her makes you the give-way vessel under Rule 13; a narrow channel removes the privilege under Rule 9; and with the engine running you are a power-driven vessel yourself, sails or no sails.
How do I tell whether risk of collision exists?
Watch the bearing. If the direction holds steady while the range closes, the courses meet at one point. Without a bearing compass, use a shroud or a stanchion as a sight. Rule 7 says to assume risk exists whenever there is doubt.
I am under sail and overtaking a motor boat. Who gives way?
You do. Rule 13 overrides everything in the section: the overtaking vessel keeps out of the way of the vessel being overtaken, whatever either of them is doing. You are overtaking whenever you come up from more than 22.5 degrees abaft the other vessel's beam — at night, when you see only her sternlight. If in doubt, Rule 13(c) tells you to assume you are overtaking and to act accordingly.
What do I do when crossing if the other vessel is on my starboard side?
You keep out of the way, and Rule 15 asks you to avoid crossing ahead of her. Turn to starboard and pass astern: the alteration is then large enough to be obvious from the other bridge, which is what Rule 8 requires. A small change of course reads as no change at all.
Two yachts on the same tack. Who keeps clear?
The windward one, closer to the wind; the leeward yacht stands on. If you are on port tack, she is to windward and her tack is unreadable, you keep clear — Rule 12(a)(iii).
Does sail still have priority in fog?
No. Rule 19 applies to vessels not in sight of one another and knows neither give-way nor stand-on vessels. The duties are identical for everyone: safe speed, engine ready, signals, lights, readiness to stop.
Where to go next
All forty-one rules, each with a plain-language retelling, live under "Learning → COLREGs", where the search understands a rule number and a situation alike — "sailing vessel to starboard", "overtaking", "fog". For your own case the "Who gives way" builder is faster: pick your vessel, the other one and how they are placed, and out comes the answer with the rule reference and a diagram you can switch to a night view.
At night half the job is identifying the vessel before any of this applies. Read "How to read ships' lights at night: what you see and what it means", then practise in "Learning → Lights and shapes" and in the lights trainer. Short guides to those screens are "The COLREGs", "Who gives way", "The catalogue of lights and shapes" and "The lights trainer". When passing clear is not enough and you need to talk it through, the "Phrases" and "Radio" screens help, along with "What to say on VHF in a marina: ready-made phrases explained".