You are in the oceans of North America, 70 million years ago.

The water was unnaturally still, the deep blue of the Cretaceous ocean stretching out in all directions. You hung suspended, holding your breath, as a massive shadow emerged from the abyss.

It was a Plotosaurus—a 13-meter long monster, yet astonishingly graceful, perfectly adapted for speed. Its long, narrow body, covered in small, shark-like, scaly skin, cut through the water with almost no effort. The creature’s grey-bluish back blended with the gloom, while its pale underbelly seemed to catch the faint sunlight filtering down. You stayed absolutely still as its huge, curious eyes—designed for seeing in the deep—turned toward you…