There is not a single scientific explanation about why dolphins jump in the air.

Some of the theories include:

– Dolphins jump in the air to save energy as it consumes less energy traveling through the air than through the water.

– Dolphins jump to locate some other pod or to find food by looking at the water for signs of food like feeding birds or any other indication of food location.

– Dolphins do it to communicate to other dolphins or pods to hunt together or for another purpose.

– Dolphins jump only for fun.

– Dolphins jump to get rid of parasites.

Dolphins can make a large range of different sounds using a unique part of their anatomy called nasal air sacs.

Such air sacs are located just behind their blowhole.

They produce three different varieties of sounds.

Whistles.
Modulated in frequency and usually used for communication.

Burst-pulsed sounds.
Also used for communication.

Clicks.
Used for echolocation. A burst of clicks is called a click train.