In or near an area of restricted visibility, by day or night:
- (a)a power-driven vessel making way through the water — one prolonged blast at intervals of not more than 2 minutes.
- (b)a power-driven vessel underway but stopped and making no way — two prolonged blasts in succession every 2 minutes.
- (c)a vessel not under command, restricted in her ability to manoeuvre, constrained by her draught, a sailing vessel, a vessel fishing, and a vessel towing or pushing — one prolonged followed by two short blasts every 2 minutes.
- (d)a vessel being towed, or if more than one the last vessel of the tow if manned — one prolonged followed by three short blasts every 2 minutes, sounded immediately after the towing vessel's signal where practicable.
- (e)a pushing and a pushed vessel rigidly connected sound the signal of a power-driven vessel.
- (f)a vessel at anchor — rapid ringing of the bell for about 5 seconds every minute, a vessel of 100 metres or more also sounding the gong aft; she may in addition sound one short, one prolonged and one short blast to warn of her position.
- (g)a vessel aground — the anchor bell signal plus three separate and distinct strokes of the bell immediately before and after the rapid ringing.
- (h)a vessel of less than 12 metres is not obliged to give the above signals but, if she does not, shall make some other efficient sound signal every 2 minutes.
- (i)a pilot vessel on duty may in addition sound an identity signal of four short blasts.