Kingdom of the Oceans Season 1 Episode 4

Many species of land creatures found their way back to the seas, requiring another round of evolutionary adaptation. Some became full time sea-dwellers, like whales and dolphins, who outclass predator fishes. Others became amphibious, like Galapagos iguanas, or nest and bread on land, like penguin colonies, who as birds also gave up flying. On the other hand, various sea creatures with gills, like crabs and even some fishes, regularly seek food on land.