One major difference between these two animals is that the Killer Whale is a mammal but The Great White Shark is actually a fish. The Killer Whale has lungs and needs to breathe air. To do so, the Killer Whale has a breathing hole on top of its head. The Great Whale Shark, on the other hand, has gills which absorb oxygen from the water when it swims forward. The shark does not have to come to the surface of the water to breathe.