Using a ROV (Remotely Operated Vehicle) is not as easy as just throwing it over the side of the survey boat. There are a number of different factors that need to be taken into account. The ROV is attached to the boat by a line that serves four purposes. It enables the ROV to be retrieved by the team after a dive. The line also contains wires that deliver power to the ROV. It contains the video feed coming live from the ROV. Last, it means that the ROV can be remote controlled by the team on the boat.
As the ROV is attached to the boat, it's important that the boat is moored or anchored, so that the line doesn't snap. On larger research ships, a system known as 'dynamic positioning' is used. This is like having little thrusters that keep the ship in a constant position and is useful in areas where it is too deep to anchor.