Sound Signals
Short and long blasts, and bell/gong signals, used for manoeuvring and in restricted visibility under Rules 32–37.
Altering course to STARBOARD
Made by a vessel in sight of another when altering course to starboard. Only used in inland waters in some jurisdictions for agreement.
Altering course to PORT
Made by a vessel in sight of another when altering course to port.
Operating ASTERN PROPULSION
Engines are going astern. Note: the vessel may still be moving ahead through the water.
DANGER / DOUBT signal
Five or more rapid short blasts. Used when in doubt about the intentions of another vessel or when collision risk is imminent.
Power vessel underway (FOG)
One prolonged blast (4–6 seconds) every 2 minutes. Also used when approaching a bend in a narrow channel.
Power vessel stopped, no way (FOG)
Two prolonged blasts with about 2 seconds between them, every 2 minutes. Vessel is underway but has no way through the water.
Sailing / NUC / RAM / CBD / Fishing vessel (FOG)
One prolonged + two short blasts every 2 minutes. Used by: sailing vessels underway, NUC, RAM, constrained by draft, fishing vessels.
Vessel being TOWED (FOG)
One prolonged + three short blasts every 2 minutes. Sounded by last vessel in tow if manned.
Intend to overtake — YOUR STARBOARD side
Two prolonged + one short blast. The overtaken vessel sounds the same to agree, or danger signal to disagree.
Intend to overtake — YOUR PORT side
Two prolonged + two short blasts. Agreement is the same signal echoed back by the vessel being overtaken.
Vessel at ANCHOR (FOG)
Rapid ringing of bell for about 5 seconds every minute. Vessels 100m+ also sound a gong aft. May also sound one short, one long, one short blast as a warning.
PILOT VESSEL signal
Four short blasts. Sounded by a pilot vessel when on pilotage duty, in addition to the prescribed fog signal.
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