Sediment patterns on the ocean floor of the continental shelf can be studied using ultrasonic sonar systems, in which the geophysical patterns are mapped on a permanent paper record. Housed within a streamlined fish-like towed body, a transmitter sends an ultrasonic acoustic beam towards the sea bed, illuminating a path of the sea floor of width 1 km parallel to the track of the ship. The strength of the echo reverberation signals increases progressively through the sediment series soft mud, sands, cobbles, rocks and corals, so some measure of sediment identification is possible.