"Whales are the largest species of exclusively aquatic placental mammals".
Like all mammals, whales breathe air into lungs, are warm-blooded (i.e., endothermic), breast-feed their young, and have some (very little) hair. The whales' adaptions to a fully aquatic life are quite conspicuous. Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two blowholes and toothed whales have one blowhole
Dolphins are certain aquatic mammals related to whales and porpoises. Dolphins are widely believed to be amongst the most intelligent of all animals, Dolphins often leap above the water surface, sometimes performing acrobatic figures. They are capable of diving up to 260 m deep and 15 min long, but rarely stay underwater longer than few minutes.
Dolphins are social animals, living in so called schools of up to a dozen animals. In places with high abundance of food, schools can join temporarily forming aggregations of over 1000 dolphins.
