A special mark (yellow buoy), if lighted, may exhibit which light rhythm?

A special mark, which is often represented by a yellow buoy, serves a unique purpose in navigation. If this buoy is fitted with a light, it may exhibit a flashing light rhythm. This type of light signal is characteristic of special marks and helps mariners to identify the mark’s function, distinguishing it from others, like lateral or safe water marks.

Flashing lights are used because they provide a clear and recognizable cue for the navigator, as the rapid bursts of light can be seen from a distance and signal that the marker indicates something special or specific to navigation that does not relate to conventional channel marking or safe water identification.

Other light rhythms, such as Morse "A," which consists of a short flash followed by a longer flash, or occulting lights, where a fixed light is interrupted by periods of darkness, are not typically used for special marks. Equal interval lights, which shine with equal time intervals of light and dark, is also not standard for these buoys. Hence, the flashing light rhythm aligns perfectly with the purpose of a special mark, ensuring it stands out to help guide navigators accurately through a waterway.