A waterspout is a rotating column of air over a body of water.
Many waterspouts are fair-weather waterspouts that develop beneath growing cumulus clouds in relatively weak wind environments. They often begin as a dark spot on the water, followed by a visible spray ring and a funnel extending downward from the cloud. Their life cycles can last from minutes to longer periods.
Tornadic waterspouts are different: they form from severe thunderstorms and are essentially tornadoes occurring over water. Fair-weather waterspouts usually have weaker rotation, but they can still threaten boats, swimmers and coastal communities.
A waterspout is not defined simply by a cloud funnel. The circulation must connect the cloud base with the water surface. If a tornado moves from land over water, it may become a waterspout; if a waterspout reaches land, it may be described as a tornado depending on its structure and development.