References and Further Information: 1  Morrissey, J.F. and J.L. Sumich. 2012. Introduction to the Biology of Marine Life (10th Edition). 2  University of California Museum of Paleontology. Bilateral (left/right) Symmetry.
A lot of things. For one, Whale sharks are fish and use gills to breathe. Blue whales are mammals. The blue whale is also bigger than the whale shark. The tail structure is also different if you watch the whale shark swim, it uses its tail in a side to side motion while the blue whale uses a up and down movement.
Whales sharks are the largest fish in the world. They are not whales; they are sharks. They have a lot in common with whales, though. For example, they are massive like whales and they feed more like whales than a typical shark. Size & description Whale sharks can grow up to 40 feet (12 meters) long, but on average they grow to 18 to 32.8 feet (5.5 to 10 m) and weigh 20.6 tons (18.7 metric tonnes).