Top 10 Creepy Underwater Facts That Will Terrify You

You might think twice before your next trip to the beach. Welcome to WatchMojo and today we’ll be counting down our picks for the Top 10 Underwater Facts That Will Make You Never Want to Swim Again.

For this list, we’re looking at all the freakiest facts about the world’s bodies of water.

Sea monsters are frightening, but far more dangerous are the things hiding in the water too small for the human eye to see. By just swimming in the shallows, you could contract potentially deadly pathogens, from cholera to Legionnaire’s disease to flesh-eating bacterial infections in freshwater. The good news is many of these conditions can be avoided by being careful not to swallow water and washing thoroughly in clean water after swimming. But seafood is also a common culprit behind food poisoning in saltwater, which happens when it hasn’t been cleaned and prepared properly. Remember though that while these microbes might be dangerous to humans, many are vital for the ecosystem.

Though it covers over 70% of the Earth’s surface, the oceans are chronically unexplored; there are a few reasons why. For a start, people just aren’t as excited about exploring the deep sea as they are about going to Mars, as interesting as all the ocean’s strange inhabitants are. Secondly, there isn’t the potential for profit like there is with space, which means it’s not being funded as much as NASA or other space agencies are. We’ve mapped only 5% of the ocean while we’ve already got significantly more detailed maps of the moon and Mars.

One reason why it’s so hard to get to the bottom of the sea is that the deeper you go, the more intense the pressure is. This is because of the crushing weight of all the water above you, which only increases the further down you are. We’ve conquered obstacles like the lack of air with submarines and diving equipment, but it’s much harder to limit the amount of pressure placed on even the best submersibles, which is why much of deep-sea exploration is done by cameras and robots. Every 33 feet you descend, you add one entire atmosphere of pressure. At Challenger Deep in the Mariana Trench, the pressure is more than 1500 pounds per square inch.

These brainless organisms come in all shapes and sizes, and many of them won’t hurt you at all. But if you can’t tell them apart, it’s always better to err on the side of caution and stay away. While you may find the deadly and distinct Portuguese man o’ war near the surface, it’s not a single organism like most other jellyfish. It’s dangerous of course, but you should also be wary of the most venomous jellyfish out there: the box jellyfish, since it can swim as opposed to most others that just float. But many box jellyfish aren’t venomous either, which makes them even more dangerous since it’s unlikely that anyone who isn’t a professional will be able to tell a harmless one from a killer.

Many of the deadliest storms in the world, including hurricanes and cyclones, form over the oceans. In fact, a storm is only called a “hurricane” if it forms over a tropical ocean basin. It’s the warm ocean waters in the tropics evaporating that creates these storms, and it’s the reason tropical storms can’t sustain themselves when they make landfall. One of the deadliest storms in history was Typhoon Haiyan that struck Southeast Asia, primarily the Philippines, in 2013, causing over 6300 deaths in just that country. And the hurricane with the highest recorded wind speed was Hurricane Patricia, which struck Mexico in 2015, with wind speeds of 215 miles per hour.

This is a great place to go if you want to grab a quick bite to eat – if you’re a shark, that is. If you’re human, you’ll want to stay far away from this spot in the Pacific Ocean, where great white sharks frequently gather. Luckily, it’s in the middle of nowhere, located between Baja California and Hawaii, so you probably won’t come across it by mistake. The “café” was only discovered by tracking tagged sharks, and for a long time the reason was mysterious; some thought the sharks were going there to mate, but young sharks are raised much closer to the coast. The best explanation is that they’re going to feed – so it really is like a restaurant.

The speed of light through a vacuum is over 186,000 miles per second, but through deep waters, this slows down significantly. After a certain point – around 656 feet – light is simply unable to penetrate the water. This means that the vast majority of the ocean is in complete darkness, the so-called “midnight” or aphotic zone. This is one more barrier to exploring the sea, but it’s not an obstacle for the creatures designed to live down there. Some animals have bioluminescence. But for others, it’s the eyes. The reason fish have such large eyes relative to their body size is to see through this gloom, which is why many deep-sea creatures haven’t evolved to be blind - in fact, the giant and colossal squids have the biggest eyes in the animal kingdom.

The ocean has always been home to enormous creatures, able to grow to huge sizes because they have such vast habitats to roam. After all, the largest creature on Earth today is the blue whale, and luckily they’re gentle giants. But the deep ocean has historically given way to many myths and legends about enormous sea monsters, from sea serpents to krakens, and there may be some truth to these tales. We’ve found fossils of giant, marine creatures like megalodons and mosasaurs, while living creatures like the ghastly frilled shark may be responsible for serpent sightings. And there’s no telling what other huge monsters might be hiding in the unexplored deep.

One of the most elusive creatures roaming the oceans today is the giant squid, which is so mysterious that it was never photographed alive until as recently as 2002. Before this, we only knew they existed from specimens washed up on shore, sightings at sea or from other animals’ stomachs. Even in the 21st century, very few videos of giant squids in their natural habitats exist, due to the fact they’re thought to live very deep beneath the ocean’s surface. And because they’re so difficult to study, we don’t actually know the maximum size a giant squid can grow to, though the biggest squid recorded by scientists was over 42 feet long.

Before we unveil our top pick, here are a few Honorable Mentions:

Mountains
There’s a Massive Mountain Range at the Bottom of the Atlantic

Black Holes
These Whirlpools, or Eddies, Are Deadly & Closer to Those of Outer Space Than You Might Think

Great Barrier Reef
It’s the Largest Living Structure on the Planet & Can Be Seen from Space

Great Blue Hole of Belize
You Should Steer Clear of These Bottomless Sinkholes

Bloop
This Strange Sound Recorded in 1997 Has Stumped Scientists for Years; Was It Really an Ice Quake, or a Sea Monster?

Humans have been sailing the seas for thousands of years, and in that time we’ve generated an estimated three million shipwrecks. Many of these wrecks belong to ships that have disappeared, and most will have had crew aboard. This means that when you’re swimming in the ocean, you’re undoubtedly surrounded by human remains. Creepier still, you probably won’t even know; less than 1% of these wrecks have been explored, and others are completely undiscovered. Even if you go out of your way to try and avoid these “skeleton crews”, you’re probably never too far from some bones.