.......Dolphins are a group of sea animals that are close relatives to the whales and porpoises.  Dolphins are not fish, though they live in the sea. They are mammals.
They feed their young milk produced in  the mother’s body.  Dolphins have lungs and are warm-blooded meaning its body temperature stays the same regardless of the outside environmental temperature.  Dolphins, along with whales and porpoises, belong to a group called Cetaceans. Dolphins have a beaklike snout and cone shaped teeth.  Marine dolphins live in all oceans and most inhabit only salt water. River dolphins live in fresh or slightly salted water.   

McCarthy, Carolyn. dolphinpair.jpg. July 2005. Pics4Learning. 8 May 2008 <http://pics.tech4learning.com>