Whales are mammals that live in the ocean like fish, but they are very, very different from fish.
One of the biggest differences between whales and fish is that whales need to breathe air. They have lungs, and they need to come to the surface of the water often for air. Their blowhole is like their nose, which is on top of their heads. It is located on the top of their head so that the whale can breathe fresh air without coming very far out of the water. Before a whale dives under the water, they will take several deep breathes - just like you would do before diving under the water.