A newly released video from a small underwater vehicle found something quite surprising: A swarm of thousands of crabs all headed in the same direction, 1,263 feet deep in the Pacific Ocean, according to Motherboard. And it looks like something out of your worst nightmare. Or, if you’re a scientist who studies this type of thing, it’s a dream come true.

The scientists who captured the video have no idea what the crabs are doing, where they’re headed, or why they’ve all decided to move at the same time. “It was unusual. In the past, we’ve noticed aggregations of breeding crabs hanging around the ocean floor, or migrating onto land if they’re terrestrial,” Jesús Pineda, a researcher at the Woods Hole Oceanographic Institute (WHOI) told Motherboard. READ MORE