22.35 Sound signals in restricted visibility

In or near an area of restricted visibility, by day and by night, the following signals must be used:

(a) subject to rule 22.35(b)—

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

(ii) a power-driven vessel underway but stopped and making no way through the water must sound two prolonged blasts in succession with 2 seconds between them at intervals of not more than 2 minutes:

(b) the following vessels—

(i) vessels not under command, vessels restricted in their ability to manoeuvre, vessels constrained by their draught, sailing vessels, vessels engaged in fishing, vessels engaged in towing or pushing another vessel; and

(ii) vessels engaged in fishing at anchor and vessels restricted in their ability to manoeuvre when carrying out work at anchor;

must sound three blasts in succession, namely one prolonged followed by two short blasts, at intervals of not more that 2 minutes:

(c) if crewed, a vessel towed or, if more that one vessel is towed, the last vessel of the tow, must sound four blasts in succession, namely one prolonged followed by three short blasts. This signal must be made at intervals of not more than 2 minutes, and where practicable, be made immediately after the signal made by the towing vessel.

(d) when a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit, they are to be regarded as a power-driven vessel and sound the appropriate sound signal as described in rule 22.35(a):

(e) a vessel at anchor must ring a bell rapidly for about 5 seconds at intervals of not more than 1 minute and—

(i) if the vessel is 100 metres or more in length, the bell must be sounded in the forepart of the vessel; and

(ii) immediately after the ringing of the bell the gong must be sounded rapidly for about five seconds at the after part of the vessel.

A vessel at anchor may additionally sound three blasts in succession, namely one short, one prolonged, and one short blast to give warning of its position:

(f) a vessel aground must give the bell signal, and (if required) the gong signal, prescribed for a vessel at anchor in rule 22.35(e),

AND in addition must give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell.

A vessel aground may also sound an appropriate whistle signal:

(g) a vessel of—

(i) less than 12 metres in length is not obliged to give any of the signals prescribed in this rule;

(ii) 12 metres or more in length but less than 20 metres is not obligated to give any of the bell signals prescribed in paragraphs (e) and (f) of this rule,

but if the vessel does not give any such signal, it must make some other efficient sound signal at intervals of not more than 2 minutes.

(h) When engaged on pilotage duty, a pilot vessel may in addition to the signals prescribed for power-driven vessels (rule 22.35(a)) or vessels at anchor (rule 22.35(e)), sound an identity signal consisting of four short blasts.