It has become apparent that I somehow have never discuss whale evolution of the most primitive kind. After searching all of the posts here I noticed that there were none concerning what is often considered the most primitive amphibious step towards cetaceans: Ambulocetus natans. One of the transitional fossils that shows a bridge between land mammals and the ocean-going Cetacea, Ambulocetus was an amphibious shoreline or swamp dweller that was equally at home on land and in the water, but not truly a master of either. As their descendants became more attuned to the water, they would leave the land, but these fossils truly show adaptations to both the land and the water. It is thought that Ambulocetus may have hunted like crocodiles, ambushing prey from below in the water, or by staying extremely still on land. Unlike crocodiles, swimming was effected by use of apparently webbed fore and hind limbs.