Search and rescue tasks for drowned persons on the bottom of rivers or coastal seabeds are quite demanding for conventional ROVs (Remotely Operated Vehicles). Since the water current is sometimes fast, the ROV tends to drift and the cable of the ROV tends to become tangled with debris at the bottom. It has thus been reported that in most cases scuba divers conduct search and rescue tasks with no ROV support. This paper proposes a new type of ROV, Anchor Diver III, that can solve the problems of conventional ROVs. Similar to holding the leash of a running dog, Anchor Diver III uses thrusters to drive away from the mother ship, so that the wire connected between the robot and the mother ship is kept tightened during the entire operation. This paper details the development of Anchor Diver III and underwater experiments. It also gives an overview of Anchor Diver III and describes search and rescue activities during 2011 Tohoku Earthquake and Tsunami April 19–21, 2011.

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