Part C — Lights and shapes

COLREGs Rule 25: Sailing vessels underway and vessels under oars

Rule 25 says a sailing vessel underway shows sidelights and a stern light; under 20 m it may combine them in a masthead tricolour. A yacht motor-sailing by day must show a cone, point down, forward.

What Rule 25 says

  1. A sailing vessel underway shows sidelights and a stern light.
  2. Under 20 m, these may be combined in one lantern (a tricolour) at or near the top of the mast.
  3. A sailing vessel may also show two all-round lights at the masthead, red over green, but not together with a tricolour.
  4. Under 7 m: if practicable show the sailing lights; if not, have a torch or lantern showing a white light ready to show in time to prevent collision. A vessel under oars may do the same.
  5. A vessel under sail and also propelled by machinery shall show, forward where it can best be seen, a cone with its apex downwards.

This is a plain-English summary, not the official wording. For the exact text, see the IMO convention. In UK waters the rules are given legal force by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations.

What it means on a yacht

The tricolour is efficient and seen from further away, but switch to the deck-level sidelights and stern light when you start the engine. By day, hoist the motoring cone whenever the engine is driving you with sails up.

Lights and shapes under Rule 25

  • Sailing vessel underway Rule 25

    Sidelights and a stern light, no masthead light. Motor-sailing by day, show a cone point down forward.

  • Sailing vessel under 20 m, tricolour Rule 25

    Sidelights and stern light combined in one lantern at the masthead. Never use it with the engine running.

  • Sailing vessel, optional red over green Rule 25(c)

    All-round red over green at the masthead, in addition to sidelights and stern light. 'Red over green, sailing machine'. Never combined with a tricolour.

  • Sailing under 7 m, or under oars Rule 25(d)

    If she can't show sidelights and stern light, she must have a white torch or lantern ready to show in time to prevent collision.

  • Sailing vessel motoring (motor-sailing) Rule 25(e)

    With the engine running she is power-driven: masthead light, sidelights and stern light at night, and a cone point down forward by day.

Drawn from the starboard side at night, with the day shapes below. See every aspect in the lights and shapes trainer.

Practise it

Test yourself on who gives way in the free COLREGs trainer, or print the rules of the road cheat sheets for the chart table.

Other rules in Part C

Frequently asked questions

What lights does a sailing boat show at night?

Red and green sidelights and a white stern light. Under 20 m they may be combined in a tricolour at the masthead. Optional red-over-green all-round lights may be shown at the masthead, but not with a tricolour.

What is the motor-sailing cone?

A black cone, point down, shown forward by day by a vessel under sail that is also using its engine. It tells others that you are a power-driven vessel under the rules.