Device for measuring in real time sea currents in deep water

A device for measuring in real time sea currents, or current meter, comprising a plunger dropped from a boat and descending to the bottom of the sea, drifting with the currents, wherein N acoustic responding buoys B.sub.1, B.sub.2, . . . B.sub.i, . . . B.sub.N with N.gtoreq.3 are lowered to the bottom of the sea and positioned geographically, the boat comprises means for transmitting acoustic pulses at frequency f under the control of a clock H.sub.1, the plunger comprises means for receiving these pulses at frequency f as well as means for transmitting a practically instantaneous response at frequency f.sub.E and a response delayed by time T at frequency f, buoys B.sub.1, B.sub.2, . . . B.sub.i, . . . B.sub.N responding to the pulses at frequency f by pulses at frequencies f.sub.1, f.sub.2, . . . f.sub.i, . . . f.sub.N, all these frequencies being different, the boat comprising means for receiving at frequencies f.sub.E, f.sub.1, f.sub.2, . . . f.sub.i, . . . f.sub.N and a computer for calculating from the time of reception of the different pulses, the coordinates of the plunger in relation to a system of coordinates tied to the responding buoys and wherein said computer determines the currents as a function of the depth.