Did you know that whales are the largest animals that have ever lived on earth, and the largest animals living in the ocean. They are even larger than the largest dinosaur, and it is believed that millions of years ago whales probably walked on land. Over time, their hind legs disappeared and their front legs became flippers. Blue whales can weigh over 150 tons and be over 100 feet long. Humpback whales are also large, weighing up to 45 tons. Humpback whale flippers can be as long as 15 feet.