17 Most Alarming And Horrifying Underwater Sea Facts


The beauty of the sea is undeniable, but that open water is one of the scariest places on earth. It’s freezing cold, dark, and filled with potential predators lurking around every corner. The concept of the unknown is also what makes it so terrifying — beneath the surface of the water are countless mysteries, many of which haven’t even been discovered by our species yet. Although images of the deep sea have been released, there’s nothing like being in the presence of it — standing over it and looking into inky depths, it can feel like the darkness is going to eat you up at any moment. Or one of the sharks that live inside of it. Here are the scariest and most shocking deep sea and ocean facts that will send chills down your spine.

1. The majority of the ocean’s plastic pollution isn’t because of consumer items like shopping bags, straws and other consumer products as we’ve been taught. Instead, the majority of it comes from fishing nets and fishing gear.

2. Only 5% of the entire ocean on our earth has been discovered. That’s 95% of the deep, inky sea that’s completely unaccounted for. We wonder what else is going bump in the night…

3. When a whale dies, it creates an entirely new ecosystem. In a way, a whale becomes its own world when it passes on.

4. The Mauna Kea Volcano in Hawaii is the tallest mountain underwater. It’s also the highest volcano in Hawaii, sitting 6000 meters beneath the ocean’s surface and standing a whopping 4000 meters above. Starting from the ocean floor, its overall height is 10,000 meters.

5. There’s a lake underneath the ocean called the “hot tub of despair.” It’s very highly concentrated with salt and has dissolved methane — if any creature enters it, they die.

6. At a certain depth underwater, buoyancy shifts. This means that you start getting pulled down rather than floating up towards the surface. Yikes!


7. In a Youtube interview with a military diver, he revealed that during covert ops, a lot of time is spent just hanging out underwater in the dark until it’s time to make a move. He mentioned that the job required him needing to get used to large creatures bumping into him while in pitch-black surroundings. Yup, that’s a nope from us.

8. Here’s a gross, little-known fact: lost sailors or anyone clinging to ship wreckage in the sea will have their skin dissolved by salt water if soaking for over three days. That’s something you don’t see in the movies!

9. The largest biomass migration happens every night when creatures of the deep sea come up to feed.



10. The Gulf Stream is created by ice melting from the north polar ice cap. With global warming, that ice cap is quickly disintegrating. Once it disappears, so does the Gulf Stream, and the weather for the entire northern hemisphere changes completely.

11. The sonar that humans use for deep sea mapping is terrible for underwater species, specifically whales, porpoises and dolphins. It ruins their own sonar abilities, interfering with their ability to navigate and communicate.

12. A scuba diver wrote that the scariest thing about diving at first is that you hear way more underwater than you do above the surface. Besides the shifting of water, the sounds of fish clicking and other sounds of creatures underwater are magnified. Underwater sounds move and travel much more, so you hear more and “much quicker” according to the diver.


13. There are tons of impeccably preserved shipwrecks from ancient Greece at the bottom of the Black Sea. The depth of the water makes it anoxic, or oxygen-free and hence preserves organic materials such as wood.

14. The harsh reality of the ocean is that when you dip your toe in the water, you immediately lose your place at the top of the food chain.

15. The ocean is one of the most violent forces out there. While it’s not actively trying to kill people, it’s a strong force that can sweep you under forever if you’re not paying attention — one wave can mean the end of a life, but it’s just business as usual for the vast sea.

16. The loudest unidentified underwater sound was recorded in Point Nemo, which is the most isolated place in the world. It’s located in the middle of the South Pacific gyre, a huge rotating current that keeps out nutrient-rich water, so no life can be found there.

17. There are more viruses in the ocean than stars in the Milky Way.