If whale evolved from mammal, why they similar to fish?

First of all they don't have fins, they have flippers, which house finger bones just like in your hands, it is very much like a hybridization of fin and hand. The flipper at the rear is attached to the tail. They do have a tail. There is "residue" like the left over hip bones even though there are no rear legs left over. read more

Whales are mammals that have acquired the necessary adaptations for living underwater. They are similar to fish only in that they can swim and have the same general shape, ideal for moving underwater. read more

Whales, dolphins, porpoises, seals, walruses, and many other marine animals are mammals, not fish. The marine mammals exist because about 50 to 60 millions of years ago, some mammals wandered off of the land and into the ocean, and there they evolved into different types of marine mammals. read more

Though these creatures, such as Dimetrodon, looked like reptiles, they were actually the archaic precursors of mammals. By the time the first mammals evolved 200 million years ago, however, dinosaurs were the dominant vertebrates. read more