The footage was captures by researchers studying biodiversity at the Hannibal Bank Seamount off the coast of Panama.
The expedition’s chief scientist Doctor Jesus Pineda, a biologist at Woods Hole Oceanographic Institution (WHOI) called the encounter “unexpected” and “mesmerising.”
The team captured the video of the crab swarm during a dive in the manned submersible Deep Rover 2 on the last diving mission of the month-long expedition in April 2015.
Dr Pineda said: “When we dove down in the submarine, we noticed the water became murkier as we got closer to the bottom.”
VIDEO: This army of marching crabs will make your skin crawl