You are in the coastlines of England, 155 million years ago.

You are just standing by the rocky shore over a shimmering, warm, shallow lagoon, with limestone reefs visible below, and flocks of small pterosaurs soaring around the skies, when you spot something unusual in the water.

It is a sleek, roughly 3-meter-long creature with a streamlined body, smooth green skin, and long jaws filled with sharp teeth glides through the water. It resembles a mix between a crocodile and a dolphin, using a shark-like tail to propel itself.

It spots a shoal of small fish close by. It rapidly closes the distance, snapping its long, thin jaws—specialized for catching slippery prey—and snatches a fish.