Whales are mammals that live in the ocean. They are viviparous, usually giving birth to one calf per litter, and they nurse their calves with milk. But many people classify them as fish, but in fact they are not fish but mammals. Distributed in all oceans of the world.

Whales are viviparous mammals, not fish. A baby whale needs breast milk for a year to mature. Fish are oviparous vertebrates. Parent fish generally do not have the habit of taking care of small fish. The whale's "fins" actually evolved from its limbs. Fish are not. Whales breathe with their lungs. Fish breathe through gills. Whales are endotherms, while fish are ectotherms. The presence or absence of fish scales cannot be used to distinguish whales from fish.