Pacific spotted dolphins swim gracefully through sunlit water.

Lina, a dolphin pup, is pictured together with his mother, Lala, at the aquarium of the Zoo of Madrid.

A group of dolphins leap from the ocean near Kona, Hawaii.

A dusky dolphin (Lagenorhynchus obscurus) leaps from the water.

Two rough-tooth dolphins swim free after they were released about 18 miles off the Florida Keys in Key Largo, Florida. The two mammals were the last of 11 released following a stranding.

Dorsal fin of a single dolphin swimming in the Mediterranean Sea off the coast of southern Spain.

An Atlantic bottlenose dolphin sticks its head out of the water at the Mirage Hotel.

A flutist and harp player play music in front of a large fish tank full of dolphins at the Hakkeijima Sea Paradise aquarium in Yokohama, suburban Tokyo.

Two children watch a Pacific white-sided dolphin swim by at the Shedd Aquarium's underwater viewing area in Chicago, Illinois.

An Atlantic bottlenosed dolphin mother and calf swim together. Next check out a group of volunteers trying to save beached false killer whales, which is actually a type of dolphin!

Volunteers desperately try to save over 100 false killer whales beached at Dolphin Bay near Busselton, 230 kms south of Perth.

In November 2006, a bottlenose dolphin with palm- sized fins near its tail was found in Japan. The extra set of fins could be the remains of hind legs

A sleeping dolphin usually has one eye closed.

The fins help dolphins to steer in the water.

There are 37 species of dolphins, including this estuarine dolphin.

Dolphins can live up to 50 years, but typically live for around 17 years

A dolphin can use its tail to flip around and gain speed up to 25 mph!

Dolphins emit a variety of sounds to communicate with other dolphins. Like other toothed whales, they use echolocation to avoid obstacles and to locate prey

Dolphins, like other mammals, breathe oxygen from the air, but can remain under water for up to an hour.

Dolphins feed on everything from fish to squid to crabs.

Scientists think that dolphins sleep with one side of the brain resting at a time. The side that is awake controls the dolphin’s breathing. Resting one side of the brain at a time makes it possible to sleep underwater

Pregnancy lasts about a year for female dolphins. Usually only one dolphin pup is born and the pup suckles for up to two years.

Dolphins swallow fish whole, despite the 100 teeth in their mouths. The teeth are used to grasp prey.

Most kinds of dolphins can somersault, or flip head over tail.

Bottle-nosed dolphins belong to the same family as killer whales and pilot whales.