Share New research combines cutting-edge engineering with animal behaviour to explain the origins of efficient swimming in Nature’s underwater acrobats: Seals and Sea Lions. Seals and sea lions are fast swimming ocean predators that use their flippers to literally fly through the water. But not all seals are the same: some swim with their front flippers while others propel themselves with their back feet. In Australia, there are fur seals and sea lions that have wing-like front flippers specialised for swimming, while in the Northern Hemisphere, grey and harbor seals have stubby, clawed paws and swim with their feet. But the reasons why these two different ways of swimming evolved has perplexed biologists for generations. Is one style better than the other?