Dolphins live in the sea, and they swim very well, but they are not fish. Dolphins are mammals, like cows, dogs and people.
Fish breathe under the water, but dolphins need air. A dolphin breathes through a hole on the top of its head. Every few minutes it swims up to the surface to take a breath.
Baby dolphins drink milk from their mothers, just like other mammals. A mother dolphin stays close to her baby for a long time and teaches it how to find food.
Dolphins are very social animals. They live in groups and "talk" to each other with clicks and whistles. Scientists think that every dolphin has its own special whistle, a little like a name.