Restricted visibility fog signals — power-driven under way vs stopped vs RAM/NUC/fishing/towing?

Rule 35: power-driven making way — one prolonged every ≤2 min; power-driven under way but stopped, not making way — two prolonged (≈2 s apart) every ≤2 min. NUC/RAM/CBD/sailing/fishing/towing vessel — one prolonged followed by two short, every ≤2 min. Vessel being towed (if manned) — one prolonged + three short, immediately after the towing vessel, when practicable. At anchor — rapid ringing of the bell ~5 s every ≤1 min (≥100 m: bell forward then gong aft); may also sound one short–one prolonged–one short to warn. Aground — three separate bell strokes, then the anchor bell signal, then three strokes. Lead: one prolonged = making way; two prolonged = stopped; 'prolonged + two short' covers the whole restricted/constrained family.

In fog you hear 'one prolonged followed by two short'. Name every vessel it could be — and what do you do?

It could be any of: a vessel NUC, RAM, constrained by draught, sailing, fishing, or towing/pushing (Rule 35(c)). You cannot tell which from the sound alone. So treat her as a vessel you must keep clear of, navigate at safe speed with extreme caution, and be ready to reduce to bare steerage (Rule 19(e)). Trap: don't try to name a single type — the signal is deliberately shared by the whole 'can't easily get out of your way' family.

At anchor in fog you hear, from another vessel, rapid bell forward then a gong aft. What does the gong tell you?

Rule 35(g): a vessel at anchor rings the bell rapidly for about 5 seconds every minute; if 100 m or more in length she sounds the bell forward AND the gong aft. The gong therefore tells you she is a large vessel (≥100 m) at anchor. Lead: bell + gong = a big ship at anchor; bell alone = a smaller one.

Part D · Sound and light signals

COLREGS Rule 35 — Sound Signals in restricted Visibility

Q: You hear two prolonged blasts in fog. Is she moving?

Rule 35(b): two prolonged blasts (about two seconds apart), every not more than two minutes — a power-driven vessel under way but STOPPED and making no way through the water. One prolonged (35(a)) would mean she is making way. Tip: count the prolonged blasts — one = making way, two = stopped.

In or near an area of restricted visibility, whether by day or night, the signals prescribed in this Rule shall be used as follows:

(a) A power-driven vessel making way through the water shall sound at intervals of not more than 2 minutes one prolonged blast.

(b) A power-driven vessel underway but stopped and making no way through the water shall sound at intervals of not more than 2 minutes two prolonged blasts in succession with an interval of about 2 seconds between them.

(c) A vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel constrained by her draught, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts.

(d) A vessel engaged in fishing, when at anchor, and a vessel restricted in her ability to manoeuvre when carrying out her work at anchor, shall instead of the signals prescribed in paragraph (g) of this Rule sound the signal prescribed in paragraph (c) of this Rule.

(e) A vessel towed or if more than one vessel is towed the last vessel of the tow, if manned, shall at intervals of not more than 2 minutes sound four blasts in succession, namely one prolonged followed by three short blasts. When practicable, this signal shall be made immediately after the signal made by the towing vessel.

(f) When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and shall give the signals prescribed in paragraphs (a) or (b) of this Rule.

(g) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 metres or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition sound three blasts in succession, namely one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel.

(h) A vessel aground shall give the bell signal and if required the gone signal prescribed in paragraph (g) of this Rule and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may in addition sound an appropriate whistle signal.

(i) A vessel of 12 metres or more but less than 20 metres in length shall not be obliged to give the bell signals prescribed in paragraphs (g) and (h) of this Rule. However, if she does not, she shall make some other efficient sound signal at intervals of not more than 2 minutes.

(j) A vessel of less than 12 metres in length shall not be obliged to give the above-mentioned signals but, if she does not, shall make some other efficient sound signal at intervals of not more than 2 minutes.

(k) A pilot vessel when engaged on pilotage duty may in addition to the signals prescribed in paragraphs (a),

(b) or (g) of this Rule sound an identity signal consisting of four short blasts.

COLREGS Rule 35 — Sound Signals in restricted Visibility

All COLREGS Rules and Annexes

Part A · General

Part B · Steering and sailing rules

Part C · Lights and shapes

Part D · Sound and light signals

Part E · Exemptions

Part F · Verification of compliance

Annex I · Positioning and technical details of lights and shapes

Annex II · Additional signals for fishing vessels fishing in close proximity

Annex III · Technical details of sound signal appliances

Annex IV

Also free for seafarers

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