buoy

A fixed, floating object attached by a cable or chain to the seabed to mark safe channels, approaches to harbours, and dangers to navigation. Buoys made of wood are known to have been used in the Middle Ages and are probably much older; modern buoys are generally made of steel or fibre-glass reinforced plastic. Buoys may be fitted with bells or whistles, usually operated by the motion of the waves. There are also mooring buoys, used for the anchoring of ships. In addition to a battery-powered light which allows recognition at night, a buoy may be fitted with a fog signal and a racon (a radar beacon that can be identified and located by its response to a radar signal). The colour, shape, markings, and flash pattern of a buoy convey information to navigators.

A buoy is a floating device that can have many different purposes, which determine whether the buoy is anchored (stationary) or allowed to drift. lifebuoy - a life saving buoy designed to be thrown to a person in the water to provide buoyancy. Usually has a connecting line allowing the casualty to be pulled to the rescuer Submarine communication buoy - to be released in case of emergencies or for communication Communication buoy for a bottom pressure sensor, for tsunami detection. DAN buoy - has two meanings: a large maritime navigational aid providing a platform for light and radio beacons a lifebuoy with a flags used on yachts and smaller pleasure craft Sonobuoy - used by anti-submarine warfare aircraft to detect submarines by SONAR Surface Marker Buoy - taken on dives by scuba divers to mark their position underwater Decompression buoy - deployed by submerged scuba divers to mark their position underwater whilst doing decompression stops shot buoy - used to mark dive sites for the boat safety cover of scuba divers so that the divers can descend to the dive site more easily in conditions of low visibility or tidal currents and more safely do decompression stops on their ascent mooring buoy - to keep one end of a mooring cable or chain on the water's surface so that ships or boats can tie on to it tripping buoy - to keep one end of the tripping line on the water's surface so that a stuck anchor can more easily be freed weather buoy - equipped to measure weather parameters such as air temperature, barometric pressure, wind speed and direction and to report these data via satellite radio links to meteorological centres for use in forecasting and climate study. May be anchored (moored buoys) or allowed to drift (drifting buoys) in the open ocean currents. profiling buoy - specialised model which adjusts its buoyancy so that it will sink at a controlled rate to 2,000 metres below the surface while measuring sea temperatures and salinity. ice marking buoy - buoys for marking ice holes in frozen lakes and rivers, so that snowmobiles do not drive over the holes. lobster trap buoy - brightly colored buoys used for the marking of lobster trap locations so the person lobster fishing can find their lobster traps.