This slimy, pink-tongued green sea monster will haunt your dreams. But what is it?

According to National Geographic, the creepy critter is a ribbon worm, a marine creature that can swallow its prey whole. (Video: Wei Cheng Jian via YouTube)

Whaaaaat.

The video above has been making the rounds on the Internet for the past few days, with viewers understandably grossed out -- and fascinated -- by the slimy worm therein. I mean, it basically looks like Nickelodeon slime gone rogue, slithering across the ground and snaking an impossibly long pink tongue out into the air.

[Watch doctors lure a worm out of a boy’s eye with … basil?]

But the Taiwanese fishermen who spotted the creature didn't find a monster hitherto unknown to man. National Geographic reports that the creepy critter is called Lineus fuscoviridis, more commonly known as a ribbon worm.

The pink ooze is just a proboscis, used to slurp up prey. Experts told Nat Geo that it was probably out because the worm -- which had been brought up onto land accidentally -- was in distress over its dry surroundings. So that scary alien thing is actually just a distressed marine worm.

[‘Leech-nado': Scientists are working to identify the leech species swarming in this video]

But there are more than a thousand known species of ribbon worm to fret over. And yeah, they're generally pretty gnarly looking.

As it happens, another ribbon worm was the subject of a viral video just weeks ago. Remember this guy?

If you need more proof that ribbon worms should be the exclusive populace of your nightmares, Smithsonian Magazine has "14 fun facts about marine ribbon worms" that aren't fun at all. Example: Think that wibbly wobbly pink proboscis on Lineus fuscoviridis is bad? Well, it is. But cousins in the order Hoplonemertea use spike-like proboscises to stab their prey. And some use a stabby proboscis to shoot neurotoxins into their prey.

[The ‘termites of the sea’ have super weird digestive systems, and they might help us make biofuels]

And fuscoviridis is long enough to freak us out -- growing to lengths of up to six feet -- but it's a small fry.  Lineus longissimus has been measured at lengths up to 98 feet. Some believe it can grow to be as long as 197 feet, which would make it the longest animal on the planet.

Sweet dreams.

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