Swimming and diving. Dolphins swim by moving their flukes up and down. This action differs from that of most fish, which propel themselves through the water by swinging their tail fins from side to side. Dolphins use their flippers to make sharp turns and sudden stops. But they can maintain those speeds for only a short time.
Most dolphins swim much slower.
Dolphins do not usually dive deeply, though they have the ability to do so. When a dolphin dives, its lungs collapse and its heart rate slows down. These actions allow the animal's body to adjust to the increasing pressure as the dolphin dives deeper underwater. The attraction between dolphins and people goes back thousands of years. Ancient Greek artists decorated coins, pottery, and walls with pictures of dolphins, and the animals appear in Greek and Roman mythology.