You are in the oceans of Europe, 245 million years ago.

The water of the shallow Triassic sea was surprisingly warm, a bright turquoise contrast to the dark, bituminous limestone forming the seabed around me. You held your breath, watching a small, sleek shape navigate the sunbeams filtering down. It was a Mixosaurus, roughly three feet long, its eel-like body undulating with slow, calculated grace, starkly different from the rapid, dolphin-like motion of its later ichthyosaur relatives.

It paused, holding its position using a small dorsal fin, its narrow, long beak lined with tiny teeth probing a crevice in the seafloor for fish. The creature seemed curious, turning its relatively large skull to fix a glassy eye on you.