ROV - Remotely Operated Vehicle

A remotely operated underwater vehicle, commonly referred to as an ROV, is a tethered underwater vehicle. They are common in deep water industries such as offshore hydrocarbon extraction. While the traditional abbreviation "ROV" stands for remotely operated vehicle, one must distinguish it from remote control vehicles operating on land or in the air. ROVs are unoccupied, highly maneuverable, and operated by a crew aboard a vessel.

http://en.wikipedia.org/wiki/Remotely_operated_underwater_vehicle