Rules of the road: who has right of way at sea?

At sea, right of way is set by the COLREGs, the International Regulations for Preventing Collisions at Sea. Remember the logic: the less manoeuvrable a vessel, the higher its privilege — and between two power-driven vessels, the one coming from starboard stands on. Privilege never exempts you from keeping a permanent lookout, nor from avoiding a collision as a last resort.

The hierarchy of privilege: who gives way to whom

The COLREGs rank vessels from most to least privileged: vessel not under command (breakdown), vessel restricted in her ability to manoeuvre (dredging, underwater operations), vessel constrained by her draught, vessel engaged in fishing (trawls or nets deployed, not the Sunday angler trolling a line), sailing vessel, then power-driven vessel. Each gives way to everything ranked above it. A capital point: a sailing boat that starts her engine for propulsion becomes a power-driven vessel under the rules, even with every sail set. The logic of the text is crystal clear: the more easily you can manoeuvre, the more the manoeuvring falls to you.

Sail against sail: a matter of tacks

The tack names the side the wind comes from: on port tack, the wind arrives from port and the mainsail sits to starboard. Two rules are enough. One: on different tacks, the boat on starboard tack is the stand-on vessel, the other keeps clear. Two: on the same tack, the windward boat keeps clear and the leeward boat holds her course. And a third for murky cases: if you are on port tack and cannot tell which tack the other boat is on, assume you must give way and manoeuvre. These rules are identical in racing and cruising, everywhere in the world.

Power against power: the three textbook cases

First case, head-on: each vessel alters to starboard and they pass port to port, like cars on a two-way road. Second case, crossing courses: the vessel that sees the other coming from starboard gives way — in other words, traffic from your right stands on. Third case, overtaking: the overtaking vessel keeps clear, always and without exception — a sailing boat overtaking a motorboat must keep clear of her, theoretical privilege notwithstanding. In every case, the manoeuvre must be bold, wide and early: the other vessel must understand your intention at a glance.

Narrow channels, traffic schemes and big ships

In a narrow channel, vessels under 20 metres and sailing boats must not impede those that can only navigate safely inside the channel: cargo ships, ferries, pilot boats. Traffic separation schemes (the "motorways" of busy waters) are crossed with your heading at right angles to the traffic flow. With big ships, forget theory: a freighter at 18 knots covers a mile in three minutes twenty, with a blind spot of several hundred metres ahead of the bow and almost no ability to stop. In practice you pass astern, and you never "test" your privilege against 200 metres of steel. If you are unsure of having been seen, a call on VHF channel 16 with your position settles the doubt far better than stubbornness at the helm.

Night lights: reading intentions in the dark

At night, lights tell the whole story: red to port, green to starboard, white at the stern, and one or two white masthead lights for power-driven vessels. A few standard readings: a lone green means you see her starboard side, she is crossing your course; red and green together, she is coming straight at you; a lone white, you are overtaking her — or it is a vessel at anchor; red and green with no masthead light is a sailing boat. The vital reflex, day or night: a steady bearing with decreasing range means risk of collision. And slow down: at night, speed is the one variable you control completely. Go deeper with our night sailing guide.

Where to start: making the reflexes stick

• Learn the four standard situations by heart: head-on, crossing, overtaking, sail against sail.
• The moment doubt appears, take successive compass bearings: if they do not change, manoeuvre early.
• Manoeuvre boldly: a 30-degree course change is visible, a 5-degree tweak is not.
• Stand-on does not mean passive: hold course and speed, but the rules require you to avoid collision as a last resort. Five short blasts signal doubt or danger.
• A permanent visual and audible lookout remains mandatory; electronics help but do not replace it — see our guide to electronic navigation.
• The COLREGs are core syllabus in every licence and training scheme; the terms (tack, bearing, stand-on...) are in the glossary.