Aquatic mammals of the suborder toothed whales. Species of the dolphin family live in all open seas and sometimes enter the mouths of large rivers. Representatives of the family of freshwater, or river, dolphins have a much more limited distribution. For the most part, they inhabit inland fresh water bodies, although some of them can penetrate into brackish estuaries and even into coastal zones of the seas. Dolphins, like all cetaceans, breathe air, periodically rising to the surface.