ROV stands for "Remote Operated Vehicle". ROV's are not
submarines by definition, since they are robots controlled by
tether, by an operator stationed on a support vessel.
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Remote Operating Vehicle= (ROV), ROVs are used where a danger
exists for divers or the depth is beyond the limit for man or
manned machine.
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ROV means remotely operated underwater vehicle, so the pilot
isn't in the machine. The pilot is sitting at a control panel on a
ship nearby.