ROV is short for "Remotely Operated Vehicle
". It is used as a common name for robots that are used subsea
in the oil industry
The ROV's vary in size from a small (1ft x 1ft x 3ft) observation platforms to huge beasts (2m x 2m x 3m) meant for construction work.
They are most often shaped like cubes, as speed is not a requirement, but functionality is - the front of the ROV is often filled with 2-3 cameras and 1-2 arms. In addition there is often a retractable tool box in the front.
Most are connected to a ship or drill rig by an umbilical feeding signals and power. A team of 2-3 persons work the ROV (as supervisor, pilot and tool operator). Work-class ROV's are fitted with one or two arms, with either grabbers mounted on them, or tools.
The reason ROVs have become more popular than divers are that the equipment required to do ROV intervention is much smaller than for saturation diving. As an example: a typical ROV ship is 60 m long, and carries a crew of 30 people. A diving ship is 100 m long and crews 100 people.
Some operations are also to hazardous to risk human lives.
This includes high pressures, explosives, deep dives etc.
There are some freeflying autonomous vessels, sleek streamlined with a limited battery capacity. They are mostly used on small ships doing seabed survey. In theory they could be thrown off a pier with instructions to return in 48 hours with an accurate seabed map.