Sea hunters : dolphins, whales, and seals

Suppose you could go back in time 50 million years, to the banks of a river in Pakistan.

If you were lucky, you might see a wolf-sized creature called Pakicetus diving for fish in the water.

The animal looks like a long-legged otter with a pointed snout.

It may not seem like it, but Pakicetus is an ancestor of today's whales.