What very clearly looks like someone's large intestine that sunk to the bottom of the ocean is actually a predator and scavenger worm that can reach lengths of around six and a half feet.
Deep beneath the ice in the waters of Antarctica, this worm will eat anything dead it can find, and barring a carcass, it will kill its own food. It has a proboscis, but not the fragile little one you'd think of on the face of a butterfly. This proboscis is more like a really sharp hammer. The worm will stab its prey over and over again with its own face until the prey stops moving. Then it gets really disgusting.
Is that a side mouth?
The proboscis worm doesn't really have teeth for chewing, so it prefers the softest tissue of an animal, essentially eating its prey from the inside out. It will just poke a hole in the skin and go to town on the guts. And because they're scavengers as well, the other worms will notice the meal and wind themselves around it too until there's just a revolting knot of massive tongues all trying to lick the insides of some dead thing. Here's a video of them eating a seal by climbing through its eyes.
Thus marks the first time we wished David Attenborough would stop talking about nature.
If you're wondering how something so awful could be allowed to get so big, proboscis worms don't have any natural predators, primarily because they can secrete acid from their skin. If they ever feel threatened, they release a strong acid into the water around them that can kill any fish that's stupid enough to try to eat one of these pieces of nightmare spaghetti.
"But what's their weakness?!" you cry, distraught that your planned Antarctic snorkeling trip has hit a snag. Well, we're sorry to say that they don't really have one. If they get into a bind, they can even shape-change. Badass as they are, they're also ridiculously flexible, even by worm standards. For example, since they breathe through their skin, if oxygen levels in the water start dropping, they'll just flatten themselves out like pizza dough, giving them more surface area to breathe with and less distance for oxygen to travel. They are perfectly adapted for their environment, and while they may not be able to kill an experienced arctic diver like yourself, they will certainly be hoping you stop moving long enough for them to crawl through your orifices and eat your insides.
If your dreams aren't jam-packed enough with terror, then feel free to learn about 12 Things You'll Wish You'd Never Seen Under a Microscope and 8 Terrifying Skeletons of Adorable Animals.