A remote sensing technique or device that uses sound waves to detect, locate, and sometimes identify objects in water. The term is an acronym for sound navigation and ranging. There are many applications, using a wide variety of equipment. Naval uses include detection of submarines, sea mines, torpedoes, and swimmers; torpedo guidance; acoustic mines; and navigation. Civilian uses include determining water depth; finding fish; mapping the ocean floor; locating various objects in the ocean, such as pipelines, wellheads, wrecks, and obstacles to navigation; measuring water current profiles; and determining characteristics of ocean bottom sediments. Sound waves rather than electromagnetic waves (for example, radar and light) are used in these applications because their attenuation in seawater is much less. Some marine mammals use sound waves to find food and to navigate.