Dolphins - Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They mostly eati fish and squid. Dolphin is one of the most intelligent sea animals in the world. The biological Scientist of Atlanta University recently discovered that Cetaceans which are the marine mammals commonly known as whales, dolphins and other fishes have the sense of self respect, social activities, sadness and pleasure.