The crab survives by eating wood that has sunk to the ocean floor, comprising trunks and leaves swept into the sea, as well as the odd shipwreck.
Inside the stomach of the crab, also called a squat lobster, are bacteria and fungi that help digest the wood.
The discovery, published in the journal Marine Biology, adds to evidence that these so-called 'wood falls' help support special underwater communities.
"At first sight, it seems improbable," says PhD student Caroline Hoyoux of the University of Liège, Belgium.
"Munidopsis andamanica is a species only found in the deep sea and yet it eats 'terrestrial food'," she says.
