We know more about the surface of Venus than we do about the deepest depths of our oceans, which has led scientists to increase their studies of the ocean floor. But during a recent excursion off the coast of Panama, scientists found something they kind of wish they hadn’t.

Diving down in a submarine, Woods Hole Oceanographic Institution biologist Jesús Pineda and his team came upon a murky layer of gunk blocking their view. First they thought it was just sediment, but then they saw something move.

“As we slowly moved down to the bottom of the seafloor, all of the sudden we saw these things,” Pineda recalled.

01-crab-swarmVimeo / Woods Hole Oceanographic Inst.

“At first, we thought they were biogenic rocks or structures. Once we saw them moving — swarming like insects — we couldn’t believe it.”

02-crab-swarmVimeo / Woods Hole Oceanographic Inst.

Watch their hair-raising discovery in action.

These are called Pleuroncodes planipes, otherwise known as tuna crabs, and are typically found around Baja California. Makes you wonder what else is happening in our oceans that we don’t know about!

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