Now open wide...

Just a little wider...

That's it.

Grows like goliath, hunts like a tiger and swims like a fish. The Goliath Tigerfish lurks the waters of the Congo River system and several other lakes in southern Africa. This fish is remarkably adept at swimming and killing due in part to an air-filled sac in its body that allows it to detect vibrations from animals in the water. Those razorsharp spikes in its mouth may also help the cause.

Many thanks to dear reader John C. for shoring up this goliath creepy animal.

I don't think you're ready for this Jelly.

Game over, jellyfish. Play again. And again. And again. And again...

Turritopsis dohrnii just won’t quit. The aptly named Immortal Jellyfish is the only creature in the world that can revert back to its juvenile form after reaching sexual maturity. How, you ask?

The process is called transdifferentiation, whereby one type of cell is transformed into another type of cell. The Immortal Jellyfish can do this with its entire body.

The adult Immortal Jellyfish looks and floats like…a jellyfish. But when conditions aren’t ideal, it turns into a “blob-like cyst”, anchors to a surface and undergoes reverse metamorphosis back to its juvenile form as a mere polyp. It’s like a full-grown frog turning back into a lowly tadpole.

Scientists believe it can repeat its life cycle indefinitely. Since they’re constantly cheating death, the Immortal Jellyfish are now spreading from their native Caribbean to waters all over the world.

Photos via Peter Schuchert and Nat Geo

Caution: Wide Load.

We all know the sea is thick with fish. With so many different species, some are bound to be a little unsightly. It’s basically a numbers game, and the Asian Sheepshead Wrasse happens to be a victim of the odds. This fish swims the shallow waters around China, Japan and the Koreas while resembling a very old man. With bulging protrusions on its head and jaw, this is a face only a mother could love.

Waitaminute. Is that my grandpa swimming in the ocean?

Photo via Arkive

Watch it swim:

Under a veil of creepiness, an octopus swims.

The allure of the unique Blanket Octopus is its poetic defense mechanism. When the Blanket Octopus is threatened, a gorgeous scarf-like webbing unfurls from a set of arms tucked within its body, making the animal appear large, intimidating and creepy to potential predators.

Snooze. We’d rather see a blast of jet-black ink in the face. Who’s with us?

This would totally go with that new blazer I just bought.

Watch the blanket in action, accompanied by proper English voiceover work:

The Glass Squid: a whole lot of nothing.

Okay class, now who can tell me where the brain is located? Anyone? Anyone know the answer?

Neither do we. But we do know the Glass Squid is one very creepy animal with not much going on. Transparent skin, ridiculously short arms, telescopic eyes and a enormous sack of emptiness. That’s it. Class dismissed!

This is naut pretty.

The Nautilus is yet another living fossil we’re very fond of. These cephalopods haven’t evolved very much in the past 500 million or so years, which makes them creepy, old and faithful. Just the way we like our animals.

Its trademark coiled shell contains many, many chambers and is pressure-resistant to 2600 feet below. The Nautilus swims via jet propulsion and osmosis. Using its siphon, it draws water into its main living chamber, then pushes it out. While water is inside the chamber, a thin organ running through all the chambers extracts the salt. The salt diffuses into the blood and the Nautilus adjusts buoyancy by pumping gas and fluid into or out of the chambers.

The end result of this biological song and dance? It moves through water.

The living quarters contain many chambers. How quaint.

Half animal, half plant, 100% creepy.

This Green Sea Slug (Elysia chlorotica, specifically) is the official Underwater Curiosities category challenger on Creepy Animals. We ask:

It is Underwater?   Yes.

A Curiosity of sorts?   Why yes.

Creepy?   Most definitely.

An Animal?   Hmm. Not exactly.

That’s because Elysia chlorotica creates chlorophyll, just like a plant. It accomplishes this task by harvesting the genes and photosynthesizing organelles from the Vaucheria algae it ingests. This means the slug is fully equipped to manufacture it’s own food via photosynthesis, which has never been observed in the animal kingdom. It also means that once a young slug eats its first full meal, it never has to eat the algae again.

This one goes straight to heaven.

Behold the Sea Angel. A gorgeous, otherworldly creature seemingly made of gossamer and light in equal parts, gracefully beating its wings as it soars through waters deep. Then you realize it’s actually a snail without a shell. Now it’s a creepy animal. Congratulations.

Dun dun. Dun dun. Dun dun dun dun dun dun dun dun.

This is so much worse than a Great White lurking on the beaches of Amity Island. Sawsharks are most obviously distinguished from other sharks by the row of teeth sticking out on either end of its long snout, which it uses to blade its victims.

Observe:

Muahahahhaaa.

Sawshark on Wikipedia