A combination of a gimbaled vertical geophone and a hydrophone used together. The natural frequencies and damping coefficients of the hydrophone and geophone are matched. The device is attached to or contained within an ocean-bottom cable (OBC) (q.v.) that is deployed on the sea floor. The signals from the hydrophone and geophone are recorded separately at each receiver station and are combined in processing to attenuate ghost reflections and water-column reverberation.