Here's why:
* Breathe air: Whales have lungs and breathe air just like humans and other mammals. Fish, on the other hand, use gills to breathe underwater.
* Give birth to live young: Whales give birth to live young, which are then nursed with milk. Fish lay eggs.
* Warm-blooded: Whales are warm-blooded, meaning they can regulate their own body temperature. Fish are cold-blooded, meaning their body temperature changes with the surrounding water.
* Hair: While whales don't have much hair, they do have a few bristles around their mouths. Fish lack hair altogether.
So, even though whales live in the ocean and have a streamlined body shape, they are actually more closely related to land mammals!