There is a kind of soft, toxic snail that lives in the sea called a Nudibranch. The many kinds of Nudibranch all have intense coloration and weird shapes — so weird, in fact, that National Geographic just devoted an entire gallery to the strange creatures. See below for more multicolored, deep-sea weirdness worthy of Cthulhu's spawn.
According to National Geographic:
Nudibranchs crawl through life as slick and naked as a newborn. Snail kin whose ancestors shrugged off the shell millions of years ago, they are just skin, muscle, and organs sliding on trails of slime across ocean floors and coral heads the world over.
Found from sandy shallows and reefs to the murky seabed nearly a mile down, nudibranchs thrive in waters both warm and cold and even around billowing deep-sea vents . . . So why, in habitats swirling with voracious eaters, aren't nudibranchs picked off like shrimp at a barbecue? The 3,000-plus known nudibranch species, it turns out, are well equipped to defend themselves. Not only can they be toughskinned, bumpy, and abrasive, but they've also traded the family shell for less burdensome weaponry: toxic secretions and stinging cells. A few make their own poisons, but most pilfer from the foods they eat. Species that dine on toxic sponges, for example, alter and store the irritating compounds in their bodies and secrete them from skin cells or glands when disturbed. Other nudibranchs hoard capsules of tightly coiled stingers, called nematocysts, ingested from fire corals, anemones, and hydroids. Immune to the sting, the slugs deploy the stolen artillery along their own extremities.
But sometimes even the vicious Nudibranchs must find time for love. That's what you're seeing right here, with two Nudibranchs getting busy.
Find out more about these dangerous but recycling-conscious snails, and see over a dozen more pictures in the full gallery at National Geographic.
Photographs by David Doubilet for National Geographic.