What does 'Masthead light' mean?

The term 'Masthead light' refers specifically to a white light that is fixed at the highest point on the vessel's mast. According to the COLREGs (International Regulations for Preventing Collisions at Sea), a masthead light serves as an important navigation light visible from different angles and across significant distances. It helps other vessels to ascertain the presence, heading, and direction of the vessel at night or under conditions of reduced visibility. The placement at the top of the mast maximizes visibility for approaching vessels.

Other options do not accurately describe the function or characteristics of a masthead light. The reference to a red light visible from behind pertains to a different type of navigation light, while the idea of a light that can change angles does not align with the fixed nature of a masthead light. Similarly, a colored light indicating navigation status relates to other types of navigation lights described in the regulations, such as sidelights or stern lights, rather than the specific function of the masthead light. Thus, the correct understanding of a masthead light lies in recognizing it as a fixed white light at the top of the ship's mast, serving a clear purpose in maritime navigation.