Abstract: Buried ocean cable is irradiated with a suitable sonar signal, and in response emits distinct characteristic "signature" backscatter signals. The "signature" signals are distinct for specific individual constructions of cable, and therefore assist in determining the identity of a buried object without having to dig it up. Search apparatus launches the unique sonar signal toward the buried cable, with a predetermined beamwidth, attack angle, cross-section, and signal character. The signal consists of a succession of bursts of different frequencies, separated by a step function, for example, and separated by silent periods. The signal is repeated as the search vehicle travels a predetermined direction with respect to the estimated cable orientation. The backscatter signals are received by the sonar apparatus for analysis by digital comparison to a data library of known signal patterns, or for display on an operator's monitor.