Only a few creatures that abandoned the seas for land ever went back: the ancestors of whales, sea turtles, and ichthyosaurs, to name several. But—with the notable exception of the semiaquatic Jurassic Park III baddie Spinosaurus and its kin—even fewer dinosaurs took the plunge. That’s why a new fossil unearthed in south-central Mongolia is making waves. The long-legged dinosaur stood about 45 centimeters tall (the height of a modern goose) some 71 million to 75 million years ago, and likely used its many teeth to grab and hold fishy prey. Halszkaraptor escuilliei, like Spinosaurus, had long bones at the tip of its snout, which was thick with a network of nerves and blood vessels—a feature present in aquatic reptiles from ancient plesiosaurs to modern-day crocodiles. A long, flexible neck—about the same length as the creature’s body—helped it sneak up on prey, the researchers assert today in Nature. And that long neck, as in Spinosaurus, shifted Halszkaraptor’s center of gravity forward, forcing it to adopt a more-erect posture when walking, much like shorebirds of today. Another sign that Halszkaraptor was semiaquatic, the researchers say, lies in the creature’s stubby forelimbs; the shape of some bones there hint that they were used to maneuver when swimming.