An ROV is a sort of underwater robot, a deep-sea television camera and lights surrounded by six motors that move it up, down, backwards, and forward.   It looks like a small submarine, the camera visible through the transparent pressure dome.

We use the JWFishers Sea Lion.  This is the top of the line of the JWFisher ROVs, with extra horsepower to work against currents and for towing a long umbilical. 

The unit is rated for 500 feet depth.  We have two umbilicals.  One is 250' and the other is 1000' long.  Four 100-watt lights are mounted on the ROV.  We have two TV cameras.  Both are commercial grade, high resolution.  One is color, and the other is B&W.  The B&W camera needs only .7 lux illumination, so is best in water that has a lot of suspended particulate matter.  (Such matter reflects the ROV's lights much like car headlights can sometimes be useless in a fog.)