You are in the oceans of North America, 36 million years ago.

The water of the Tethys Sea was impossibly warm, a shallow, turquoise world dotted with mangrove islands where the Sahara Desert would one day be. You hung just below the surface, letting the gentle current take you.

Suddenly, movement. Through the sun-dappled water, a sleek, five-meter shape accelerated toward me, stopping only a few feet away. It was a Dorudon.

It wasn't quite a dolphin, though it acted like one. Its face was longer, filled with a crocodile-like arrangement of sharp, interlocking teeth—a "spear-tooth" designed for gripping fish. Its back was curved and smooth, ending in a powerful tail with a fluke, but the way it moved felt… ancestral. As it turned, You saw them: tiny, vestigial hind flippers, useless for swimming but a stark reminder of a terrestrial past.

It watched you with curiosity rather than hunger, breathing loudly through its nostril at the surface before diving down to chase a school of fish. For a moment, you were surrounded by a small pod of them, clicking and moving gracefully, fully aquatic yet inherently primitive.