A research team studying marine biodiversity at the Hannibal Bank Seamount off the coast of Panama stumbled upon quite the underwater party: thousands of red crabs swarming en mass in low-oxygen waters just above the seafloor. Scuttling around at a depth of 385 meters (1,263 feet), the researchers think they were hiding from predators at the time.

As they note in their study, published in the journal PeerJ, seamounts are ecological “hotspots,” home to a range of creatures and organisms. Just 1 percent of all of these seamounts – essentially underwater hills – have actually been studied, meaning that many may hide animals or behaviors that are currently unknown to science.

This study, detailing the nature of the mob-like crowd of crimson crustaceans, appears to be an excellent example of this.

Hannibal Bank Seamount Expedition from Woods Hole Oceanographic Inst. on Vimeo.

“As we slowly moved down to the bottom of the seafloor, all of the sudden we saw these things,” Jesús Pineda, a biologist at Woods Hole Oceanographic Institution (WHOI) and chief scientist on the expedition, said in a statement. “At first, we thought they were biogenic rocks or structures. Once we saw them moving – swarming like insects – we couldn't believe it.”

Although this type of behavior has been documented before – on Christmas Island, for example – this new video shows it can happen outside of this isolated strip of land in the Pacific Ocean.