Steve looks at the most graceful fish in our seas. Manta rays may not look like sharks, but they are part of the same family. Steve swims with them off the coast of Hawaii, observing how their wide, flexible, cartilage skeleton enables them to summersault through pockets of plankton, hovering it up. Back in the Shark Lab, Steve reveals the secrets behind how they glide and fly through the water so effortlessly.