Ambulocetus ("'walking whale'") was an early relative of whales that could walk as well as swim. It lived during early Eocene epoch of the Paleogene period, some 50-49 million years ago in Pakistan.
During that time Pakistan was a coastal region of India, which was a large island in the Indian Ocean.
Ambulochetus was 3 meters (10-foot) long and a mammalian crocodile. The back legs Ambulochetus were better adapted for swimming than for walking on land and the creature probably swam by undulating its back vertically, as otters and whales do. Ambulocetus did not have external ears. To detect prey on land, they may have lowered their heads to the ground and felt for vibrations. It has been speculated that Ambulocetids hunted like crocodiles, lurking in the shallows to snatch unsuspecting prey. It is known that it was able to move between salt and fresh water.