A buoy is a floating device used in water to mark locations, provide navigation assistance, or indicate hazards. They are often brightly colored and can be made from materials like plastic or metal. Buoys are commonly found in oceans, lakes, and rivers, helping boaters and swimmers stay safe. There are different types of buoys, such as navigation buoys, which guide vessels through channels, and mooring buoys, which allow boats to tie up without anchoring. Some buoys are equipped with lights or sound signals to enhance visibility, especially at night or in poor weather conditions.