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. These sounds leave the animal's body through the melon, an organ on top of the head.