Abstract: The invention relates to a method for determining, for a detector placed on the surface of the seabed, the vertical propagation time and the velocity of propagation in the water of a wave emitted from an emission point. The method includes: emitting a wave from the emission point; recording the wave received by the detector; determining the vertical propagation time by, where tdir is the direct wave propagation time between the emission point and the detector, and tmul is the propagation time of the first multiple wave between the emission point and the detector; and determining the velocity of propagation of the wave, where X is the distance between the emission point and the water-surface point that is vertical to the detector.