Rule 28 - Constrained by draught

Please note: The following information has been reproduced from Part C (Lights and Shapes) of the Prevention of Collision at Sea Regulations 1983 (external link). The purpose of the reproduction is to explain "graphically'' the requirements of navigation lights on a variety of vessels.

A vessel constrained by her draught may, in addition to the lights prescribed for power-driven vessels in Rule 23 (power driven vessels), exhibit where they can best be seen three all-round red lights in a vertical line, or a cylinder.