It is lighter than water, and so it probably also helps dolphins stay afloat. Like all other mammals, dolphins have lungs. The animals must surface regularly to breathe air and usually do so once or twice a minute. A dolphin breathes through a blowhole, a nostril on top of its head. The animal seals its blowhole by means of powerful muscles most of the time while underwater.
Dolphins have a highly developed sense of hearing.
Dolphins also have good vision, and the entire surface of their bodies has a keen sense of touch. All these senses function well both above and below the surface of the water. Dolphins have no sense of smell. Dolphins have a natural sonar system called echolocation, which helps them locate underwater objects in their path. A dolphin locates such objects by making a series of clicking sounds.