There are many different species of dolphins. A familiar one is Flipper's kind, the bottlenose dolphin. One of the world's most endangered species is a dolphin called by many names such as Beiji; Pai C'hi; Chinese River Dolphin; Yangtze Dolphin; Whitefin Dolphin; Whiteflag Dolphin. It inhabits the Yangtze River in China. It is said that these animals are very close to being extinct since there are only 5 of them left, whereas in 1984 there were 400.

Warm-blooded like men, dolphins are mammals, not fish, and they give birth to one baby at a time, nursing their young up to four years. They live in social groups called pods and interact with each other very closely. These pods' make-up can change, since dolphins interact with dolphins from other pods from time to time. A lone dolphin that has lost his friends at sea can easily be adopted by another pod.

Dolphins have powerful tails that not only help to steer them in water, but also signal annoyance or danger. Just like humans, dolphins like to gesture when they interact with each other. To communicate, they use body language or they whistle and they stroke one another with their fins as if bonding socially. When they swim together as friends, they move synchronously leaping in and out of the water. When they are angry or aggressive, they open their mouths or clap their jaws violently.

Dolphins can dive to great depths and also can leap high over the water. Being mammals, they need to breathe, but unlike humans their breathing is voluntary. They breathe through the opening on the top of their heads. It is possible that dolphins can drown. When that happens other dolphins come to the drowning dolphin's aid, supporting his body in such a way that his blowhole stays above the water.

To sleep, dolphins have to shut down only half of their brain, which probably means that they are always alert to danger. Dolphins also take short naps as they float just below the surface. Yet, unlike humans, their most active feeding time is the night, although they spend a good amount of the day looking for food.