Cetaceans are marine mammals with a torpedo-shaped, virtually hairless, body. They have special ways of navigating through water.
Dolphins have a well-developed biosonar system.
Knowing this is important if you want to understand how bottlenose dolphins find their way around in the water. Bio is a rootword that means life. Sonar means sound. This sound comes from their nasal sac system - their nose. The sound they make travels as waves.