Animal behaviourists theorise that there are several reasons why dolphins jump, though few studies have been conducted to interpret this particular behaviour. Dolphins jump over 20 feet above the water, and they do seem to like the activity, because they do it even when there is no apparent functional reason.
Dolphins jump to travel, because that uses less energy than swimming through the water. Water is much more dense than air, and with their streamlined bodies, a dolphin can make a good deal of progress with one long jump.
Dolphins are smart -- they are often found moving along in the bow (back) wave of a boat, letting the wave momentum carry them forward rather than expending their own energy.
They also jump in an attempt to find food, similar to the way birds scan for fish from above the water. In addition, if they have found a school of fish while swimming, they sometimes jump to scare the fish to pack tighter into their group, making more fish easier to catch.
Dolphins learn to perform jumps as a reward for fish from humans, an activity which is common at aquariums, where they do shows for audiences.
An adult dolphin can eat 13.6 Kilogram of fish in one day.
Dolphins jump as a way of communicating with other dolphins. A study by the University of Otago in New Zealand found that certain types of jumps appear to communicate motivation to other dolphins, or to signal the beginning or end of travelling.
Dolphins also communicate through various vocal sounds such as whistling and clicking. They splash as a warning of danger.
Dolphins might jump to shake off parasites such as barnacles or sucker fish. In addition, they also may jump to escape small attacking sharks.
Male dolphins do flips and spins out of the water when mating, and behaviourists think this is either a show of dominance by the males to keep other males away, or else playfulness as part of a courtship ritual. Some of these manoeuvres are quite complex, and may be a way for males to attract females.
Dolphins may jump simply because it's fun. Spinner dolphins, for instance, leap from the water and do several corkscrew spins before hitting the water again. This may be an effort to shake off parasites, but some scientists believe it is just playful behaviour.
The Red Sea Dolphin Reef in Eilat, Israel, provides tourists with a rare opportunity to observe dolphins up close in their natural habitat. Here, the dolphins are not bribed with food to perform tricks or interact with humans, yet they play with the staff and jump for the guests, and it seems they do it simply because they are sociable and happy.