Pyura chilensis is a creature that not only looks like a rock, but is also completely immobile like one, too. It eats by sucking in water and filtering out micro-organisms. Its blood also produces a rare element called vanadium.
It is born male, but becomes hermaphroditic at puberty. It also reproduces by tossing clouds of sperm and eggs into the surrounding water and hoping they knock together.
Locals of Chile or Peru (where it's found) eat it raw or in stews. They say it tastes “soapy” and "bitter."