Side scan sonar towfish. Side Scan Sonar Model MK-300 (Sound, Navigation and ranging), was a tool with a very important impact on oceanography research. It was used to map the seafloor in a simple way using the acoustic property of sonar. This tool has the ability to capture hundreds of metres of seafloor on each side of the sonar, towed behind a moving vessel.

Sonar works by transmitting a narrow fan-shaped acoustic pulse perpendicular to its direction of travel, emitting sounds and listening for the reflections as the pulse hits solid objects. This build an image of the seafloor. The travel time of the returned pulse is recorded together with its amplitude as a time series and sent to a topside console for interpretation and display. The topside console stitches together data from successive pulses, creating a long continuous image of the seafloor as the side scan sonar is towed from a survey vessel.

The first commercial Scan Sonar was made in 1970 by Martin Klein in Cambridge, Massachusetts, United States. Sonar has a wide range of uses including marine archaeology, oil and gas industry, fishery research, dredging operations, environmental studies, military applications and geological surveys.