A buoy is a device which is designed to float on the water, either in the open ocean or in a navigational channel such as a bay or river. Buoys have been used in navigation for hundreds of years, and they serve a multitude of functions, ranging from warning systems to alert navigators to dangers like reefs to data collection devices for government weather agencies like the National Oceanic and Atmospheric Administration (NOAA) in the United States. If you have ever visited the seaside, you've probably seen a buoy.
The word “buoy” entered the English language in 1296, and it appears to be derived from an Old French word, buie, meaning “beacon,” a reference to one of the important functions of a buoy. Around the worlds, buoys are used as navigational features to help people locate hazards, harbors, and other features of interest or concern. By international agreement, buoys all over the world use the same color codes and symbols to ensure that they can be universally understood.
In a heavily trafficked area, buoys may be used to mark out shipping lanes, ensuring that boats know where to go and reducing the risk of collisions. A buoy can also be used as a mooring device, allowing boats to anchor themselves without needing to be attached to a dock. Some divers and casual sailors take advantage of mooring buoys to anchor their boats while they dive, swim, or fish.
Buoys are also extremely valuable as scientific devices. Many nations use buoys to collect data about the movements of the ocean and the weather, using this information to provide weather forecasts and to learn more about regional weather conditions. Buoy data is typically broadcast on a public radio frequency for the benefit of surfers, swimmers, and sailors who might want to know about unusually high swells or incoming storms.
A buoy can also be used as part of a tsunami warning system. Buoys typically keep track of changes in water level, and a sudden drop which can signal a tsunami will usually result in a prompt communication with a central monitoring center, allowing agencies to warn people about incoming tsunamis and storm surges. Thanks to years of collection data in some parts of the world, buoys can determine whether a change in water level is cause for concern or not.
Many buoys have bells, horns, or lights to assist with navigation. Belled buoys are useful because they require no power to operate, and they can be heard when they can't be seen, which can be useful along foggy, dangerous costs. Some buoys have foghorns which are capable of projecting across a long distance to warn mariners about reefs, shoals, and rocky coastlines.