A device to warn a ship crew of submerged objects in their immediate vicinity, combined with alarm and logging facilities. The device is composed of one or more sonic or ultra sonic transducers placed aboard the ship, with coverage arranged so as to give surrounding "envelope" to the sides and to the...http://www.google.fr/patents/US5303204?utm_source=gb-gplus-shareBrevet US5303204 - Submerged object warning and logging system
