Sound signals study overview

Interpret manoeuvring, danger, anchor and restricted-visibility signals.

Practise observation and judgement using sailing scenarios. Interactive questions and your device-local progress load when JavaScript is available.

Study points

• A power-driven vessel making way through the water sounds one prolonged blast at the prescribed intervals in restricted visibility.
• Under the restricted-visibility signal rules, an underway power-driven vessel making no way through the water sounds two prolonged blasts.
• One short blast indicates an intended alteration to starboard; two short blasts indicate port and three indicate operating astern propulsion.
• The danger signal calls for immediate attention and a reassessment; it is not permission to continue an unsafe manoeuvre.
• A vessel at anchor sounds the prescribed rapid bell ringing; larger vessels have additional gong requirements.
• In restricted visibility, use safe speed and engines ready; if danger is indicated, reduce speed and proceed with extreme caution.
• The Rules define a prolonged blast as four to six seconds; a short blast lasts about one second.
• Three short blasts indicate operation of astern propulsion under COLREG Rule 34(a). This describes the propulsion being used, not necessarily the vessel’s resulting movement.

Educational revision only. Check current official rules, charts and publications before navigating.