The Moody Institute of Science film explores the nature of sound in the deep sea. The film charts the early use of undersea hydrophones to listen to sounds beneath the sea, and the invention of sonar at the 6:00 mark. At 6:17, hydrophones at Chesapeake Bay are shown in 1942, used for national defense, detecting croaker fish. At 7:58, Moody Science explorers are seen getting into a deep sea diving suit to record the first ever underwater sound motion picture. At 10:00, the University of Rhode Island's Narragansett Marine Laboratory is seen, cataloging hundreds of sounds made by different species using a spectrograph. At 13:40, dolphins are seen performing at Marineland, and a study shown of a dolphin's ability to distinguish items underwater is made using sonar. At 20:30, humpback whales are seen producing underwater calls. At 22:54, a Nagra or similar tape recorder is seen being used in the field to record underwater sound in the arctic.