The Pelagia noctiluca or edible mauve stinger is an invasive species that is currently clogging up the waters of the Med. In response, chefs are discovering ways to prepare it (first step is to remove the poisonous stinger by boiling it and plunging it into ice water). It (apparently, we haven't tried it) tastes a bit like oysters. Chopped and fried in batter it becomes medusa fritta.
Images by: Hans Hillewaert, Creative Commons License