To precisely position a sea surface-side ultrasonic transceiver onto a measuring instrument on the sea bottom without setting a marking buoy by utilizing the communication between the sea surface-side transceiver held by a marine vessel and the measuring instrument set on the sea bottom to guide the marine vessel.

Various hydrographic phenomena data are measured by a measuring instrument 1 using ultrasonic wave which is set on an intended sea bottom, transferred to a sea bottom-side ultrasonic transceiver 2 through a cable 2a, and accumulated in a memory part. When the measurement data is recovered, a marine vessel 5 loading a sea surface-side ultrasonic transceiver 3 is guided to the measuring instrument 1-set sea surface by GPS navigation, and the transceiver 3 is put into the sea. The transceiver 3 transmits a call signal from a measurement data recovering device 4, receives the response signal from the transceiver 2 after the lapse of a prescribed time, and calculates the required time from the transmission of the call signal to the receipt of the response signal to move the marine vessel 5 in the direction of reducing the required time. The transceiver 3 can be thus approached just above the transceiver 2, or the measuring instrument 1.