You are in the oceans of Europe, 180 million years ago.

You hung suspended in the cobalt blue of the early Jurassic sea, your breath echoing in your ears, when the water suddenly seemed to tighten. A sleek, muscular form, easily twelve feet long, shot past you with the speed of a modern dolphin. It was an Ichthyosaurus.

It stopped about ten meters away, instantly turning its enormous, dinner-plate-sized eyes—easily the largest you had ever seen—directly toward you, analyzing your presence.