Pyura chilensis looks just like a rock. Anyone swimming by this Chilean sea creature might not give it a second glance. But slice into its bumpy carapace and you’ll hit slimy, tomato-red flesh that oozes clear blood.

Commercial fishermen harvest and sell the creature at Chilean fish markets, where it’s known as piure. They remove the vibrant innards and offer the meat fresh or dehydrated. Locals compare the taste to sea urchin, though it’s often described as “less delicate.” The flesh has a metallic flavor that reflects its contents: iron, titanium, and shockingly high levels of the rare element vanadium. Some critics dislike the bitterness of the metals, which they say create a “soapy” essence.

Coaster dwellers enjoy fresh, diced piure in ceviche with onion, coriander, and lemon juice. They also slice and boil it for a rice-and-salad pairing, or incorporate it with other seafood into a traditional stew called paila marina.

Piure belongs to the class of immobile, invertebrate filter-feeders known as “sea squirts,” all of which are hermaphrodites. Born male, P. chilensis becomes a hermaphrodite at puberty and can reproduce, alone or with others, by shooting out eggs and sperm that mingle together in a cloud.

Perhaps the creature’s versatile sexual abilities are why piure’s also been touted as an aphrodisiac. Yes, these living rocks might help diners get their rocks off.