Feel like going down to the beach this weekend? Don't do it. Or if you have to for some reason, don't go into the ocean. Because there are things swimming around your waters that can bite you with your own teeth. If that's not scary enough for you, by all means, plunge in!

Sheepshead: The Saltwater Fish

The fish in the video above is a sheepshead. It's also known, due to both its stripes and its personality, as a convict fish. Its teeth first start growing in when it is just over a tenth of an inch long. The tiny teeth help it eat soft-bodied prey like plankton and algae. By the time it's two inches long the sheepshead is eating barnacles. It can grow up to five pounds. And it travels in groups.


Fishers like to catch it, but it presents them with a few problems. First, it likes its prey alive and wriggling. Second, it has a number of long spines along its body that will stab anyone who tries to grab it. (The message is clear: "I inflict the pain around here.") And third, even when they have a set of tongs to handle it with and a wriggling shrimp to lure it in, the sheepshead will often bite right through their hook. That's right, in the time that it doesn't spend crushing barnacles to death, it chomps metal in half. How does it do that?

With these.

Yep, on the outside sheepshead fish look like they have human smiles. Once you open their mouths... you find they have no mouths. They just have a solid floor and ceiling of teeth. Once the front incisors have bitten through oyster shells or barnacle shells, the fish crushes the rest of the shell with the rows and rows of inner teeth. These things would impress a sarlacc.


And if the sheepshead failed to impress a sarlacc, it could change. A year-long study of captive sheepshead fed on different diets indicates that challenging the fish only makes it stronger. Sheepshead given nothing but hard-shelled prey had physiologically different teeth. The enamel on the outer layer of their teeth — the hardest substance in the body — only got thicker after a year of crushing exoskeletons.

These things are Atlantic fish, and will appear everywhere from Maine to Brazil. So if you're on the east coast and feel like dangling your feet in the water this weekend, just remember — fishermen agree that the best bait to use in order to catch a sheepshead is fresh shrimp. Go ahead. Wriggle those toes.

Pacu: The Freshwater Fish


If you think you're safe in fresh water, take a look at this and think again. This is a close relation of the piranha, except it's bigger than piranhas ever grow. It's known as "pacu," but that's a name for several different species of fish. They're omnivorous, but tend to go for seeds and nuts — food that they can use their impressive bite on. In aquariums they'll sometimes go after sticks, and, yes, fingers. One young girl was bitten badly enough to need a trip to the hospital when she put her finger in an aquarium. The fish stayed attached even when she pulled her hand out of the water.

So just don't put your fingers in an aquarium or the Amazon, right? That's no problem!

Except one of these made headlines when it was caught by a fisherman in Russia. Another one was caught in Paris. Another one was caught in Michigan. They're all over the place, and it's all our fault. Hobby collectors get pacu to raise in tanks, only to run into trouble. Not only do pacu need a lot of space to swim in, few people have any idea how big they can get. In the absence of predation and other stresses they get bigger in aquariums than they do in the wild. Faced with many large, energetic fish, collectors take them to local rivers and dump them in. This means that not only do these things look like a horror movie, they have the classic creature-feature set-up. They were dumped by their irresponsible owners and left to fend for themselves in the wild.


Just to complete the horror, pacu sightings caused a panic a couple of years ago when it was rumored that they ate testicles. An expert had mentioned, as a joke, that the fish used their teeth to crush nuts, but that they were used to clearer waters. Who knew what kind of "nuts" they would snack on in their new environment? After the joke made headlines, he hastily clarified that the fish didn't actually snack on human testicles. Fine attempt at humor, sir, but you do not show people a picture like that, ask them to imagine those teeth sinking into their testicles, and expect them to keep their heads. There are limits.

Promachoteuthis sulcus: The Deep Water Squid


To quote the best line from the Predator, "What the hell are you?" This thing is a mystery, wrapped in an enigma, wrapped in tentacles which have, according to the paper that describes it, "unique" ornamentation. Forget the tentacle ornamentation. You want to know what's unique about it? The fact that it's goddamn smiling at us.

We don't know much about this squid. Science has only ever had one example of P. sulcus, and you're looking at it. What we do know is that it's a kind of Russian nesting doll of horror. The outer layer is the unusual tentacles. Inside are the "teeth," which, as it turns out, are more like lips. Inside those tooth-lips is a beak, which is what the squid actually eats with. I don't know how that makes it creepier, but it does. A beak with lips. Seriously, how are we supposed to share a world with this thing?

Parrotfish: The Straight-Up Joker Smile Fish


Parrotfish get their names because they have beaks. Their incisors, over time, fused together. The beak protrudes, just slightly, and can give the fish a slightly comical smile, like that of a low-rent game show host from the 1950s. On occasion, though, the fish wears little grooves into its smile. Long cracks appear, especially at the front of the fish's mouth. And eventually, you get a parrotfish that has gone full Joker.

Maybe you still thing it looks cute. Algae don't agree with you. They've spent quite some time working out ways to live inside of coral, where they can be safe from most predators. But they're not safe from parrotfish, who bite the coral right off the reef, crush them, and eat the algae inside. The leftover bits of coral get excreted and become the beautiful white sand beaches that we admire in the tropics. To put that in perspective, that's like a monster snacking on people by eating a whole apartment building and pooping out the walls.


If you think that this sounds like the least-dangerous toothy fish of the bunch, you'd be wrong. People have pet parrot fish, and if you look on YouTube, you'll see adorable videos of these pets biting the hands that feed them. Those fish are only a few inches long. Other species of parrotfish, like the bumphead up there, get up to four feet long. Blue parrotfish, like the one just above, get two feet long. Imagine a thing that eats through coral deciding it wants to take a few nips out of you — which is what has happened to quite a few scuba divers. Parrotfish have been known to take chunks out of wetsuits. One parrotfish followed two divers for hours, darting in and attempted to bite them over and over. This one doesn't mistake us for its prey or some delicious tree nuts. This one sees that we're human and thinks, "I am taking you down."

It has been pointed out by evolutionary biologists that humans don't have special claim to squared-off incisors. We didn't even get them first. Still, there's something profoundly eerie about seeing our teeth in something else's mouth — especially if those teeth are coming towards us aggressively. Essentially, these fish are the ocean reminding us that we don't have to be around our own species to experience what it would be like to be eaten alive by cannibals. There are plenty of things that would be happy to bite us with our teeth.

As a final treat — have a look at a parrotfish tearing into a chunk of plaster of Paris, because that's the only way the aquarium that keeps it can make sure its teeth are filed down.

[Sources: Phenotypic Plasticity of Oral Jaw Dentition in Archosargus Probatocephalus, The Sheepshead Fish Has Human Teeth, Girl Needs Surgery After Piranha Bite to Finger, Pacu Panic Swallowed Hook, Line, and Sinker, A New Genus And Three New Species Of Decapodiform Cephalopods, Parrot Fish.]


Top Image: Andrea Westmoreland, Parrotfish Image: Laszlo Ilyes, Bumphead Parrotfish: Shutterstock, Nicolas Voisin 44, Parrotfish Close-Up: Shutterstock, Levent Konuk, Pacu Image: Wiki Commons, Squid Image: R Young, Sheepshead Image: VIMS.