Dolphin is not a fish, it just looks like a fish. Dolphins have no gills and are not egg-laying animals, which does not conform to the characteristics of fish. On the contrary, dolphins breathe by lungs, and the way of dolphin reproduction is viviparous. Little dolphins need adult dolphins to breastfeed to grow up. Dolphins belong to mammals.

Fish is a kind of aquatic vertebrate with variable temperature, and its whole body is covered with bone scales. It feeds on the upper and lower jaws through gill breathing, tail and trunk swinging and coordinated fin swimming. Dolphins do not have the above characteristics, so they are not fish.

Dolphin's trunk is spindle-shaped like a fish, with smooth and hairless skin, vigorous and flexible body and good at jumping and diving. It is the fastest mammal in the water.

Although dolphins live in the ocean, they are not fish, but mammals, even smaller whales. They widely live in shallow waters near the continental shelf, and most of them live in tropical warm waters.