Dolphins live in all four oceans. They also live in rivers. They eat fish and squid. They grow from 3 to 30 feet. They are related to porpoises and whales.     They are in the delphindae family. Dolphins were hunted for their skin and oil. Scientists believe dolphins are very smart.Dolphin's skin is smooth and rubbery. They need to go to the surface for air.  Every dolphin has one blowhole.       Dolphins hit sharks with their beaks to drive them away. Dolphins have great hearing, but no sense of smell. They also have a way to communicate it is called echoltion. Most dolphins travel in schools. They have torpedo shaped bodies that make them swift. They have flippers on both sides and they have a backfin called a dorsal fin. The flippers and dorsal fin help balance them. They live at least 25 years. They have different markings.