Besides being dynamic and challenging frontiers for exploration, the oceans are extremely noisy places. Land animals, such as dogs and cats, bark and meow to communicate. Fish and other marine animals also communicate with their own unique sounds. In combination, these form a confusing medley which, picked up on radar, can sound remarkably similar to the noises made by boat engines and propellers. These sounds apparently serve as communication, defense, and courtship means between the many different species of marine creatures.
Whales communicate with sounds similar to the trumpeting of elephants.
Drumfish and groupers produce drumlike thumps, probably as a defense mechanism against predators. Croakers are so called because of the hollow noises they emit. The mating call of the toadfish resembles a boat whistle. Other noisy sea animals include sea lions, seals, puffers, crabs, snapping shrimp, and lobsters.