To reduce the restrictions on the travel region of an underwater navigation object.

The underwater navigation object 1 can move underwater by power which the object itself possesses and includes a side scan sonar 10C, or the like, for collecting under-water information, and an underwater-side first acoustic modem 12H, capable of transmitting the underwater information collected by the side scan sonar 10C, or the like. A water surface moving object 2 includes a water-surface-side first acoustic modem 22H, which can communicate with the underwater-side modem 12H and receives the underwater information transmitted from the underwater-side modem 12H; and an underwater position measuring device 21 for detecting the position of the underwater navigation object 1. The moving object 2 moves on the water surface H, in matching with the movement of the underwater navigation object 1, while detecting the position of the underwater navigation object 1.

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