Shipworms have long been a menace to humankind, sinking ships, undermining piers. Now, researchers have found the first shipworm that eschews wood for a very different diet: rock. The new shipworm—a thick, white, wormlike creature that can grow to be more than a meter long—lives in freshwater.

The rock-eating shipworm does have one big thing in common with its wood-eating counterparts, however: Its burrowing may cause harm, in this case by changing a river’s course. But its burrowing does have an upside: The crevices it creates provide great homes for crabs, snails, and fish.