There are five types of buoys: navigational, mooring, storm warning, anchor, and marker.
Navigational buoys are used to mark the safe water channel for boats and ships to follow. They are usually red or green, with the top half being a different color than the bottom half.
Mooring buoys are used to tie up boats so that they do not drift away. They have a ring on top that boats can loop a rope through.
Storm warning buoys are placed in areas where there is a history of severe weather or where conditions are currently dangerous. These buoys will have flags or lights that warn boaters of the danger.
Anchor buoys mark the location of an anchor so that it can be easily found later. These buoys are often brightly colored so that they can be easily seen on the water's surface.
Marker buoys are used to mark the boundaries of a swimming area, fishing area, or other type of special zone. They may also be used to mark submerged hazards such as rocks or sunken objects.