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

The water of the Early Jurassic sea was surprisingly warm, but the fear washing over you was freezing. You were in a small, reinforced diving capsule, researching the seabed near what would become Yorkshire, when the sonar began to pulse frantically.

Through the reinforced thick glass, you saw a shape emerge from the murky blue—a Rhomaleosaurus, roughly seven meters of pure, efficient muscle. It didn't swim like the long-necked plesiosaurs you were used to; it "flew" through the water, its four large flippers moving with rapid, powerful strokes, much like a modern seal but scaled up to a terrifying degree.

It was hunting. Ahead of it, a smaller, long-necked plesiosaur—likely a juvenile Plesiosaurus—was desperately trying to dodge, its swan-like neck bending awkwardly.

The predator accelerated with surprising speed, its snout—equipped with an acute sense of smell to track prey even underwater—angled directly at the smaller creature. The smaller plesiosaur snapped at the air, its own teeth useless against the thick-skulled attacker. You also caught the glimpse of its massive, triangular head and the rows of conical teeth, aimed for the plesiosaur.

With a sudden, violent twist, the Rhomaleosaurus snapped its jaws shut around the neck of the smaller plesiosaur. I watched in silent horror as the predator thrashed, aiming to stun or kill its prey in one, brutal bite, a precursor to swallowing it whole.

The Rhomaleosaurus apparently did not notice you yet. It was too focused on its meal, and is about to turn to swim toward the deeper water, when its reptilian gaze lock onto you inside the capsule, causing you to freeze and hold your breath, realizing that you had come face to face with the top of the food chain in these Jurassic waters…