How do buoys work? They float.
There are many different kinds of buoys, and each one does a different job. There are buoys that aid in travel, commerce, weather, military operations, and other activities. Each one works in a different way, but the one thing that they all have in common is that buoys float.
Buoys, either anchored or drifting, do their jobs in deep water, and that is the big difference that separates them from land-based machines such as traffic lights at street corners or weather sensors mounted on buildings.