Side-Scan SONAR is a type of acoustic technology used for mapping the ocean floor and for tracking schools of fish. This is a well-established technique for studying marine life. Pulses of sound are projected by a ship or a towed device. As the sound waves bounce off objects, whether living things or physical features of the ocean floor, they reflect back to the ship. This generates an image of the shapes from the reflected sound. Scientists use Side-Scan SONAR to "see" in the ocean.
The Klein towfish [1], which does Side-Scan SONAR, being pulled out after a survey. (Klein Sonar Associates)
Diagram showing how a towed SONAR device works as it moves above the surface of the ocean floor. (USGS Seafloor Mapping Technology Group)
An actual SONAR-generated picture demonstrating how effective Side-Scan SONAR can be at distinguishing differences in the composition of the ocean floor. (USGS, David C. Twichell, USGS)