Dolphins are a type of marine mammal, with over 40 different types existing in various parts of the world. They are highly intelligent creatures who have attracted our attention because of their friendly and playful nature. They have been featured in films, cartoons and various myths throughout the years and are an important species in oceanic life.

Dolphins have a long body that is wide in the middle and tapers off at both ends. Towards the rear is a tail fin called a fluke that is wide and flat, used for propulsion. On the back of most dolphins is a dorsal fin. Towards the front underside are two flippers, one on either side of the body. At the end of the head of the dolphin is a snout-like beak. On top of the head is a blowhole, and on the sides of the head are holes used for hearing. Dolphins are generally some shade of gray, with lines or spots of varying other shades across their body.

A number of features are present in dolphins that help them hunt and survive. In the head of a dolphin is something called a melon. This helps the dolphin use echolocation, a skill all dolphin species are believed to have. This helps them hunt fish even when the fish are too far away to be seen. Dolphins have large brains, which make them one of the most intelligent animals in the world. Dolphins also have a keen sense of eyesight, both in and out of the water.

There are almost 40 species of dolphins that fall under 17 different genera. The genus delphinus has the two common dolphins, known as the long-beaked and short-beaked common dolphins. Simimlar dolphins include the bottlenose, Indo-Pacific bottlenose, northern and southern rightwhale dolphins. Some of the most exotic dolphins include the Chilean, dusky, Amazon river, Chinese river and melon-headed dolphins.

Dolphins are found all over the world, though their main habitat is in the shallow seawaters of the continental shelves. However, some dolphins can be found in colder arctic waters. The bottlenose dolphins and a few others prefer warm, tropical waters. Still other species of dolphins prefer saltwater or brackish waters in various major inland waterways such as the Amazon River.

Some dolphins are in danger of having their numbers thinned out thanks to human interaction. Most dolphins have no natural predators, but humans have been danger to them for many years. In 2006, the Yangtze River dolphin was considered extinct as no specimens were found, and other river dolphins around the world are also in trouble because of pollution. Certain fishing methods, such as tuna fishing or Seine fishing, hurt dolphins by catching them in nets.