This terrifying swarm of crabs has scientists baffled

There are some pretty creepy critters that live at the bottom of the ocean, but a discovery scientists made 1,200 feet below the waves in the waters off Panama is truly the stuff of nightmares. Crabs — thousands of them — are "swarming like insects" in a way scientists have never seen before.

"When we dove down in the submarine, we noticed the water became murkier as we got closer to the bottom. There was this turbid layer, and you couldn't see a thing beyond it. We just saw this cloud but had no idea what was causing it," the lead author of a paper on the phenomenon, Jesús Pineda, told The Guardian. The cloud, it turned out, was actually thousands of swarming crustaceans.

The researchers tried to find scientific literature that detailed a similar occurrence and came up empty handed. "Nothing like this has ever been seen, where we have this very dense swarm at the bottom. We have no idea why they might be doing this," Pineda said.

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The crabs were identified as red crabs, and are each about five inches long. Red crabs are not usually found so far south, or in such large numbers. Pineda called the whole thing "very unusual."

"At first we thought they were biogenic rocks or structures. Once we saw them moving — swarming like insects — we couldn't believe it," Pineda said. Watch for yourself below. Jeva Lange