You are in the oceans of Europe, 160 million years ago.

The water of the Jurassic Oxford Clay sea was a clear, brilliant blue, contrasting with the dark, silt-heavy depths below. You were suspended in the silence of the submarine submersible, watching the sunbeams dance through the water column, when the silence was broken.

A pod of ten or twelve Ophthalmosaurus swept past the viewpoint, moving with incredible speed and agility.

They were roughly 13 feet long, moving with the sleek, graceful motion of modern dolphins, though their darker, mackerel-like coloration was instantly distinct. Their eyes—massive, dinner-plate sized, and encircled by bone rings—met yours through the viewport, scanning with an intelligence designed for deep-sea hunting.

One of them broke away from the pod, breached the surface in a smooth arc, and landed back in the water, a stark reminder of their aerial-breathing reptile ancestry.