The whale shark is not related to whales.
Whales are mammals but the whale shark is a true shark and the largest fish in the world.
Its huge size is probably what gave the whale shark its name. No one knows for sure how large whale sharks grow, but they are commonly reported between 13 and 40 feet and there are unverified stories of giants over 50 feet long. Like the basking and megamouth sharks, the whale shark has an unusual way of feeding. It does not bite or chew its food. Instead, it is a filter feeder, sucking into its mouth huge amounts of water while swimming leisurely along and straining out the food over the gillrakers as the water exits through the gills.