COLREGs Rule 37: Distress signals

Rule 37 says a vessel in distress and needing help uses or displays the signals in Annex IV, such as a MAYDAY call, a DSC distress alert, red flares, orange smoke, an EPIRB, or slowly raising and lowering outstretched arms.

What Rule 37 says

1. When a vessel is in distress and requires assistance it shall use or show the signals described in Annex IV.
2. Annex IV includes: a gun fired at about one-minute intervals; continuous sounding of a fog signal; rockets or shells throwing red stars; SOS in Morse code by any method; the spoken word MAYDAY by radio; the flags N over C; a square flag with a ball above or below it; flames on the vessel; a red parachute flare or red hand flare; orange smoke; slowly and repeatedly raising and lowering arms outstretched to each side; a DSC distress alert; an Inmarsat or other ship earth station alert; signals from an EPIRB or SART; and approved radio signals.
3. Using any of these except to show distress and need of help is prohibited.

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

On a yacht, the first distress signal is usually a DSC alert and a MAYDAY on VHF Channel 16. Flares and an EPIRB or PLB are the backup if the radio fails or help needs to find you.

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 33: Equipment for sound signals
• Rule 34: Manoeuvring and warning signals
• Rule 35: Sound signals in restricted visibility
• Rule 36: Signals to attract attention

Frequently asked questions