November 1995 Diving signals
A vessel engaged in underwater operations, which includes diving operations, must carry the signals prescribed by rule 22.27(4) and (5) if she is restricted in her ability to manoeuvre. The term "restricted in her ability to manoeuvre" is defined in rule 3(g) of the International Collision Regulations. A vessel which is not so restricted must not show these signals.
Safe practice tips
Code Flag "A" of the International Code of Signals is assigned the meaning "I have a diver down; keep well clear at slow speed". This signal has advisory status only and does not give a vessel flying it any right to ignore the provisions of the Collision Regulations.
Maritime sub-rule 22.27(4) - A vessel engaged in dredging or underwater operations, which restrict its ability to manoeuvre, must exhibit the lights and shapes prescribed in rule22.27(2)(a), (b), and (c). In addition, when an obstruction exists, it must exhibit –
(a) two all-round red lights or two black balls in a vertical line to indicate the side on which the obstruction exists; and
(b) two all-round green lights or two black diamonds in a vertical line to indicate the side on which the vessel may pass; and
(c) when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shapes prescribed in rule 22.30 for vessels at anchor.
Maritime sub-rule 22.27(5) - If the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in rule 22.27(4), the following must be exhibited –
(a) three all-round lights in a vertical line where they can best be seen the highest and lowest being red and the middle light white; and
(b) a rigid replica of the International Code flag “A” of –
(i) not less than one metre in height; or
(ii) in the case of a New Zealand ship of less than six metres in length operating in New Zealand waters, not less than 0.6 metres in height, with measures taken to ensure its all-round visibility.
This rule gives statutory effect to the use of the "A" flag for the protection of divers (not the vessel).
It is emphasised that the vessel flying "A" flag must, whenever necessary, comply fully with the Collision Regulations.
Original source content - Boat Notice 141995, November: Diving signals.