Abstract: A device for measuring sea currents at great depths as a function of the depth.A spherical shaped plunger having negative floatability is dropped from a boat and descends to the bottom of the sea, releases its ballast and rises to the surface where it is recovered.Acoustic responding buoys positioned geographically receive pulses emitted by the plunger and respond. The plunger-buoy distances are determined sequentially and stored in the plunger. After recovery of the plunger by the boat a computer determines the currents at the different depths.

Abstract: A device for measuring in real time sea currents in deep water possibly exceeding 6000 m, as a function of the depth.A spherical shaped plunger having negative floatability is dropped from a boat and descends to the bottom of the sea, releases its ballast and rises again to the surface where it is recovered.Acoustic responding buoys positioned geographically as well as the contrivance receive pulses transmitted by the boat and respond to the boat. Furthermore, the contrivance also sends out a response intended for the buoys which reply to the boat; from the arrival times of these pulses, a computer on board the boat calculates the sequential positions of the contrivance in relation to the buoys as well as the velocities of the currents as a function of the depth.

Abstract: A system on board which provides measurement of flow rates of a liquid layers at different depths, the provided results being corrected from error due to the craft movement, said system being proper for location and establishment of an underwater drilling site.In this system arrangement, are combined to cooperate a Doppler sonar system providing the craft speed with respect to the sea bottom and a flow rate meter system providing the liquid flow rate by reference to the craft, a common electro-acoustic transducers unit being switched for sequential operation from sonar to flow rate system and an output data processing system derives from these two measures the values of flow rate with respect to the sea bottom.