Dolphins are social creatures and they group in pods (also called schools) of a dozen or so individuals for mating, hunting and protecting each other. Sometimes pods join temporarily in places with an abundance of food forming a superpod.

A massive Dolphin Mega-Pod of an estimated 100,000 dolphins was reported swimming together off the coast of San Diego, California on Thursday, February 14, 2013 by cruise ship captain Joe Dutra who described the pod as five miles wide and seven miles long.

The Amazon river dolphin is the largest species of river dolphin, with adult males reaching 185 kilograms (408 lb) in weight, and 2.5 metres (8.2 ft) in length. Adults acquire a pink color, more prominent in males, giving it its nickname "pink river dolphin".

Because dolphins are mammals, they need to come to the surface to breathe, but the average dolphin species can stay underwater for as long as eight to 10 minutes, and some species can remain submerged for up to 15 minutes.

The Navy Marine Mammal Program at San Diego's Space and Naval Warfare Systems Command (SPAWAR) trains dozens of bottlenose dolphins (as well as sea lions) to help the U.S. Navy. In the past, the U.S. military has used dolphins in conflicts in Vietnam and the Persian Gulf. Today, thanks to their intelligence, speed, and echolocation skills, dolphins are trained to find enemy swimmers, locate underwater mines, and guard nuclear arsenals.

Most dolphins have two stomachs, similar to a cow. One allows them to store food, and the other allows them to digest it. Those that only have one stomach have multiple chambers.

Each tail fin is called a fluke. There are no bones in a dolphin's flukes, just tough connective tissue. The dolphin uses its flukes for swimming and its flippers for steering.

Dolphin skin constantly flakes and peels as new skin cells replace old cells. A bottlenose dolphin's outermost skin layer may be replaced every 2 hours. This sloughing rate is 9 times faster than in humans. It is the reason a dolphin's skin stays so smooth and helps reduce drag when they swim.

The melon, which consists of fatty tissue and fluid, focuses and modulates the dolphin's vocalizations and acts as a sound lens, allowing the dolphin to "see" with sound.

To the untrained eye, dolphins and porpoises look nearly identical, and many people mistakenly think that porpoises are a type of dolphin. But the two species belong to completely different families and differ in their physical attributes. Dolphins are usually bigger, have longer beaks and curved dorsal fins.