Dolphins World cites five possible reasons as to why dolphins jump out of the water: to get a better view over the water, to conserve energy, to play, to get rid of parasites and to communicate with others.
Jumping dolphins gain a better view of the water and are therefore better able to locate food. Flying through the air consumes less energy than swimming through water. Jumping out of water provides entertainment and keeps their senses sharp. Parasites that accumulate on the bodies of dolphins are removed by jumping, and dolphins communicate with their mates and other pods by jumping out of water.