What is the name for a funnel-shaped cloud that rotates over water?

A funnel-shaped cloud that rotates over water is called a waterspout. It is a rotating column of air over a body of water, usually connected to a cumuliform cloud and visibly touching the surface through a condensation funnel or spray ring.

There are two main types. The more common fair-weather, or non-tornadic, waterspout is a relatively weak vortex that develops beneath growing clouds, often in tropical or subtropical conditions. A tornadic waterspout is a genuine tornado over water, usually associated with a severe thunderstorm or supercell, and can be considerably more destructive.

Fair-weather waterspouts often follow a recognizable five-stage cycle: a dark spot on the water, a spiral surface pattern, a spray ring, a visible funnel, and decay. Despite dramatic photographs, most waterspouts do not suck up large quantities of water; the visible column is mainly condensed moisture and spray. They can occur in many regions, including the Great Lakes and occasionally Antarctica.