Many people have experienced the joy of standing on a moving ship and watching a group of dolphins swim alongside. Dolphins are not only playful animals but they are also highly intelligent. They are mammals that can befound in most of the world's oceans as well as in fresh water.Dolphins can swim at speeds of up to 56 KPH and they can dive to depths of 200 meters and stay underwater for 5-8 minutes without resurfacing for air.They are well-known for the unique clicking sound they use like sonar tolocate food as well as obstacles. Every dolphin has its distinctive individual whistling sound used for communication.When dolphins sleep, they sleep in a semi-alert state by resting one sideof their brain at a time. They will help sick or injured dolphins as muchas they can, and they act as a team if there is danger.It is because of these and other human-like qualities that people have aspecial feeling for dolphins.