COLREGs Rule 33: Equipment for sound signals

Rule 33 says a vessel of 12 m or more must carry a whistle, one of 20 m or more also a bell, and one of 100 m or more also a gong. A vessel under 12 m need not carry these but must have some other means of making an efficient sound signal.

What Rule 33 says

1. 12 m or more: a whistle. 20 m or more: a whistle and a bell. 100 m or more: also a gong whose sound cannot be confused with the bell.
2. The bell or gong, or both, may be replaced by other equipment with the same sound characteristics, provided manual sounding is always possible.
3. Under 12 m: not obliged to carry these, but must have some other means of making an efficient sound signal.

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

A gas horn plus a spare canister, or a mouth-blown horn as backup, meets the rule for most yachts. Test it before you need it in fog.

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 D

• Rule 32: Definitions of sound signals
• Rule 34: Manoeuvring and warning signals
• Rule 35: Sound signals in restricted visibility
• Rule 36: Signals to attract attention
• Rule 37: Distress signals