A floating object used as an aid to mariners to mark the navigable limits of channels, their fairways, sunken dangers, isolated rocks etc., or as reference point for navigation or for other purposes. Buoys are indispensable especially on coastal waters or close to port.
- Cardinal buoy – A seamark, i.e. a buoy, indicating the north, east, south or west, i.e. the cardinal points from a fixed point such as a wreck, shallow water, banks, etc.