Expert Answer Sharks are fish, but whales are not, they are mammals. Sharks are animals of the subclass Elasmobranchia, the class Phyllochondrichma. Most sharks live in the sea, and only a few live in fresh water. Unlike other fish, the bones in their bodies are composed of cartilage, which is often calcified, but there is no real bone tissue. Whales are aquatic mammals, and they are divided into two major branches, namely baleen whales and toothed whales. There are currently 15 species of baleen whales and 75 species of toothed whales. Knowledge Expansion Whales and sharks are different creatures. Although both live in the ocean, their species, habits, breathing methods, and reproduction methods are different. The reproduction method of whales is viviparous, while the reproduction method of sharks is mostly ovoviviparous. In addition, the respiratory organs of sharks and whales are also different. Sharks breathe through their gills, while whales breathe through their mouth, nose and lungs. When a whale breathes, it first expels waste gas from its body through its nostrils, and then inhales fresh air into its lungs.