On a somewhat related note, as far as animals go, jelly fish are nuts. I mean they're barely animals at all. From wikipedia: "Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems." and, "Jellyfish have no brain nor central nervous system". No brain? I mean come on. Jelly fish are floating piles of goo with absolutely no purpose or delight in life other than being floating piles of goo. It's made weirder by how big some of them get, "Jellyfish range from about one millimeter in bell height and diameter to nearly two meters in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension." Giant brainless animals roam the ocean looking to sting and absorb prey without ever really knowing they're even doing it. They're pretty much ocean zombies.
They're nuts, and are a great example of how evolution cares about nothing but survival.