Final answer:
The North Cardinal Mark is a navigational buoy indicating safe water to the North. It is identified by its colors, top mark shapes of two upward-pointing black cones, and a quick flashing white light at night.
Step-by-step explanation:
The North Cardinal Mark indicates that there is safe water to the North of the buoy. This type of maritime buoy is part of a system used by mariners to navigate safely in coastal or hazardous waters. The North Cardinal Mark is recognized by distinctive features: it typically has a black top and yellow bottom, and its top marks consist of two black cones placed one above the other and both pointing upward. At night, the North Cardinal Mark displays a white light that flashes in a quick sequence, with a period of one second (Q 1s). It can also be marked with letters to aid in identification.