Rule 28 - Vessels constrained by their draught
A vessel constrained by her draught may, in addition to power-driven vessel lights, show three all-round red lights in a vertical line, or a cylinder shape.
Rule 29 - Pilot vessels
A vessel engaged on pilotage duty shows two all-round lights near the masthead, white over red; when underway, sidelights and a sternlight are added; when at anchor, the anchor light/shape of Rule 30 is added. A pilot vessel not on duty shows the lights of a vessel of her length instead.
Rule 30 - Anchored vessels and vessels aground
A vessel at anchor shows, where best seen: forward, an all-round white light or a ball; aft, at a lower level, an all-round white light. Vessels under 50 metres may show a single all-round white light instead. A vessel at anchor may, and one 100 metres or more must, use deck working lights. A vessel aground shows the anchor lights plus, where best seen, two all-round red lights in a vertical line and three balls. Vessels under 7 metres, when anchored outside a narrow channel or fairway, need not show anchor lights; vessels under 12 metres need not show the additional aground lights.
Rule 31 - Seaplanes
Where a seaplane cannot show lights or shapes with the characteristics or in the positions prescribed by this Part, she shows lights and shapes as closely similar as possible.
These four rules complete the night-time answer to "why is this vessel stopped or restricted".
