Part C — Lights and shapes

COLREGs Rule 30: Anchored vessels and vessels aground

Rule 30 says a vessel at anchor shows an all-round white light (two if 50 m or longer) and by day a black ball forward. A vessel aground adds two all-round red lights, and by day shows three balls.

What Rule 30 says

  1. At anchor: an all-round white light (or ball) forward, and a second, lower all-round white light at or near the stern.
  2. Under 50 m: one all-round white light where it can best be seen is enough.
  3. A vessel at anchor may, and one 100 m or more shall, also use working lights to light its decks.
  4. Aground: the anchor lights plus two all-round red lights in a vertical line; by day, three balls in a vertical line.
  5. Under 7 m, at anchor away from a narrow channel, fairway, anchorage or where others normally navigate: no anchor light or shape needed.
  6. Under 12 m and aground: the aground lights and shapes are not required.

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

Hoist the black anchor ball in the forestay by day, and switch on the all-round white anchor light at night. Leaving the nav lights on at anchor tells others you are underway.

Lights and shapes under Rule 30

  • At anchor, under 50 m Rule 30

    One all-round white light where it can best be seen. One black ball forward by day.

  • Aground Rule 30

    Anchor light(s) plus two all-round red lights. Three balls in a vertical line by day.

  • At anchor, 50 m or more Rule 30

    Two all-round white lights: the forward one higher than the one at the stern. Over 100 m she must also light her decks.

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 does a black ball on a boat mean?

One black ball forward means the vessel is at anchor. Two balls in a vertical line mean not under command, and three balls mean aground.

Do you need an anchor light on a small boat?

Yes, unless the boat is under 7 m and anchored away from channels, fairways, anchorages and other places where vessels normally navigate.