Scientists have only scratched the surface of the Earth's oceans, meaning there is a host of marine life that we don't even know about yet.
There are a lot more interesting things roaming around than just cute little fishes - but it's the things that eat them that we ought to be wary of.
Reddit users have ranked the scariest things in the sea with photographic proof that they exist, but one in particular proved to terrify people the most. Take a look here:
The fact that its named after a woman who cut off her husband's penis doesn't help matters either. But the story of John and Lorena Bobbit is for another time.
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We're talking about the Bobbit Worm - which is also known as the sand-striker or scientifically, the Eunice Aphroditois.
Its out of this world appearance is enough to spook some sea lovers, but the underwater worm has much more sinister qualities.
It looks like a cross between a snake and a centipede and is found in warm marine waters such as the Atlantic and Indo-Pacific Ocean.
This fearsome predator can grow up to three metres long, but tend to hide their humongous size to surprise their prey.
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Bobbit Worms bury their bulk deep into the seabed, leaving only their tentacles exposed.
It is covered in thick, venomous bristles which help it bury a hole and stay in there, so that unsuspecting fish have no idea of its presence. It looks more like seaweed than a murderous worm.
But its bristles have reportedly caused permanent numbness in humans - so if you ever see one, steer clear.
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Bobbit Worms have no eyes, making their reputation as the ocean's scariest inhabitant even more spookier.
Instead, they rely on five antennae on their head to sense their prey and find a meal for the night.
When some poor thing crosses its path, it springs from the sand and snaps its scissor-like jaws over its victim - often slicing it completely in half. Hence why it got it's name from Lorena Bobbit's antics.
Bobbit worms chillingly turn their muscular, tooth-studded throat lining inside out to suck the poor fishes to their doomed fate.
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Their deadly bite delivers a toxin which stuns their prey, before they drag it back to their seabed burrow to chow down on it.
Bobbit Worms also have another blood-curdling quality - they can essentially clone themselves.
They can survive attacks by splitting into multiple segments and regenerating their wounded body parts, such as the head or tail. Bobbit worms are pretty much reborn again - with a terrifying twin.
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Don't worry, you won't be the only person having a Bobbit Worm nightmare later. I'll be right there with you.
And so will a host of social media users who have well and truly been put off a dip in the ocean.
One wrote on Reddit: "Nature is f***ing terrifying," while another wrote: "Serious Tremors vibes from this thing."
A third added: "This was ABSOLUTELY the wrong thread to be reading lying in bed trying to go to sleep."
And a fourth said: "That's it, I'm never going into the ocean again."
Apparently, they can also invade at home saltwater aquariums - as they may be hiding in a piece of decor such as a large rock.
Maybe think twice about the kind of furniture your fish wants before you start decorating their home!
Olivia Burke