Top 30 Deep Sea Mysteries That Will Freak You Out

Top-30-Deep-Sea-Mysteries-That-Will-Freak-You-Out

Welcome to WatchMojo, and today we’re counting down our picks for the weirdest and most fascinating ocean-related mysteries.

#30: “Immortal” Jellyfish
Eternal life is something you usually hear about in fiction, rather than reality. However, there are some beings that have evolved to essentially live forever – even if they live in extreme conditions. Turritopsis dohrnii – better known as the immortal jellyfish – have the unique ability to return to their polyp stage when faced with something potentially deadly. While they aren’t immune to predators, they can still evade other causes of death such as old age and assault. Marine biologists are still learning more about how this process, also known as transdifferentiation, truly works, and if it can be replicated in a medical setting. It’s hard to believe that something so tiny may hold the key to one of humanity’s biggest curiosities.

#29: The HMS Daedalus’ Sea Serpent
One of the benefits of living in modern times is that many animals have been classified, quelling fears about the existence of fantastical beasts. However, for those living in the past, seeing an unknown or unidentified creature confirmed those worries. This was the case for the crew of the HMS Daedalus – who in 1848 swore they saw a large sea serpent swimming alongside their ship. They reported that it was at least 60 feet long, and was more comparable to a reptile than a fish. Some modern day specialists have asserted that they saw a sei whale – although there hasn’t been any evidence confirming that theory. Given the Daedalus’ description of its size and speed, there’s no wonder they automatically assumed it was a monster.

#28: Kaz II
Cases of disappearances on dry land are already unsettling. The thought of someone going missing while surrounded by nothing but open water is even more unnerving. In 2007, a yacht dubbed “Kaz II” was found miles off the coast of Australia. When it was searched, the team found that the entire crew – Derek Batten, Peter Tunstead, and James Tunstead – had vanished. There were signs of recent activity, including a table set for a meal. The life jackets and lifeboat were still there, indicating they hadn’t swum or ridden away from the craft. After an investigation, the authorities concluded that they had fallen off and were unable to reboard – although other ideas, such as them being stranded on a deserted island, have also been suggested.

#27: Giant Oarfish
When hearing about the things that live in the deep ocean, it’s hard to fathom that some can even exist. A fish that can grow to almost 60 feet in length and weigh over half a ton is nearly inconceivable. The giant oarfish’s size, dorsal fin, and multi-colored body helps it look more like an alien than something you’d find at your local aquarium. While some have traversed into shallow areas, they’re usually elusive. This has made it difficult to learn more about their behavioral patterns and life cycle – with research on the latter only starting in the last few years. We have the opportunity to learn more about them in real time, and when we do, it’ll be an achievement in the maritime field.

#26: The Abyssal Zone
There’s a point far enough underwater where light from the surface is no longer available, leaving everything in a state of total darkness. While that would be terrifying for any human to experience, there are some critters that have adapted to the harsh conditions – and even thrive in them. Experts are still trying to learn just how these ecosystems can be sustained in such unforgiving terrain. It’s so devoid of oxygen that many beings die if they can’t make it to a safer area. Those that survive – such as mollusks and crustaceans – have evolved to do so in various ways, such as extracting the element from higher waters. This zone hasn’t been fully explored – meaning there could be even more organisms lurking at the bottom.

#25: Abandoned Lifeboat at Bouvet Island
This discovery feels like it came straight out of a horror movie. Picture the scene – a totally abandoned island with not a soul around, the only evidence of past existence being a half-sunken lifeboat. It was discovered in the 1960s, and jump started a decades long mystery about where it came from and who could’ve been on board. A search was conducted, but there were no indications that a person had ever been there, besides the rowboat itself. It’s remained a nautical conundrum to this day, although some have theorized that it belonged to a team of Soviet scientists. While that may explain the origins of the vessel, the question still remains of who was aboard – and what happened to them.

#24: The Devil’s Sea
We’ve all heard of the Bermuda triangle, but that isn’t the only area to be wary of in the ocean. Off the coast of Japan is what’s commonly referred to as the Devil’s Sea, due to the strange and tragic things that have occurred there. With a nickname like the Dragon’s Triangle, it’s developed an ominous reputation for itself. There have been plenty of supposed cryptic activities, such as a pilot reporting an odd phenomenon in the sky before disappearing, and a ship going missing for several days. Some have claimed that these strange happenings are paranormal, while skeptics insist they must be environmental. Whether the occurrences were caused by ghosts or undersea volcanoes, it’s clear that something is amiss in those troubled waves.

#23: Bermeja
Various craft and people going missing at sea isn’t uncommon – but a whole island disappearing certainly is. Bermeja was first added to naval maps in the 16th century, after being found near the coast of Yucatán. However, after a survey taken in the late 1990s, it was discovered that the islet wasn’t in its supposed spot. Over a decade later, more extensive studies corroborated this discovery. This was baffling, as it had been recorded by multiple cartographers. So how did it disappear into thin air? There are some people who believe that something insidious occurred – namely, the CIA destroying it to aid the United States. However, there are scientific explanations that make more sense, with the most likely being heightened ocean levels.

#22: The Hadal Zone
You’ve maybe heard that we know less about the ocean than the dark side of the moon. We could have created that expression for the hadal zone, the area which lies in the deepest fathoms of the sea. Frigid cold temperatures, intensely high pressure, and barren living conditions all ensure that only the most survivalists of species live down here. These alien-like creatures shouldn’t exist, but their ethereal adaptations somehow make it possible. Its geological formations are also wondrous, sporting V-shaped trenches and submarine canyon-like depressions that could have been sculpted on Mars. Though notable explorers have reached the Mariana Trench, only a fraction of the hadal zone has ever been traversed. It holds great potential for undiscovered fantastical ecosystems…so what else is hiding there?

#21: The Mariana Trench
It’s the deepest point in the ocean at over 35,000 feet below sea level, but beyond that, what we know is limited. The Mariana Trench is a formidable area that’s teeming with biodiversity, despite being so treacherous. Here, the pressure is so intense that the only way a person could ever explore it is by drone or submarine. While we may not survive, there are some entities that have made it their habitat. Many are single-celled – although there are more complex life forms as well. There have been dozens of dives into the trench, with the bottom finally being reached in 2020. While various sights and sounds have been recorded, there are still several unanswered questions about how existence at these depths is even possible.

#20: Gulf of Mexico Shipwreck
In May of 2019, a group of researchers from the National Oceanic and Atmospheric Administration were conducting tests with underwater drones in the Gulf of Mexico when sonar picked up this mysterious wreckage. Marine archaeologists across the globe were immediately contacted to watch via livestream as the drone explored the ship. Apart from the number “2109” the researchers were unable to identify much about this ship of unknown origin. It’s estimated to have been constructed 200 years ago, and based on the charred timber, it was likely burning when it sank. What tragic fate befell this vessel? Here’s hoping we can learn more as NOAA continues to investigate. Either way, it’s in good company – the gulf is home to many such mysterious vessels.

#19: A Deadly Undersea Lake
We generally think of all water within a given space as being homogenous, but variables like temperature and the salinity levels can create entirely distinct sections – like lakes in oceans! At the bottom of the Gulf of Mexico, 3,300 feet below the surface of the ocean, researchers have found just such a body of water. 12 feet deep and roughly 32 feet across, this undersea lake might be small, but it certainly packs a punch. Dubbed the “Jacuzzi of Despair,” it kills any sea creature foolish enough to test its depths. This highly salinated water, rich in methane and hydrogen sulfide, is seriously toxic. Little is understood about this surreal undersea environment, but researchers think it might give insight into the conditions on extraterrestrial planets.

#18: Julia Sound
Recorded in 1999, “Julia” is the name given to a mysterious sound picked up by the U.S. National Oceanic and Atmospheric Administration. It only lasted 15 seconds, but it captivated the scientific community and amateur theorists alike. NOAA suggested that it most likely originated from an iceberg colliding with the landmass of Antarctica, but this can’t be proven. What we do know is that it was loud enough to resonate across a massive section of the ocean. Those willing to consider more “out there” possibilities have suggested that it could be the sound of a massive unknown creature. Rumors abound about NASA satellite photos showing a huge shadow moving in the waters off of Antarctica around that time, but no such images have surfaced.

#17: Adam’s Bridge
Rama Setu, also known as Adam’s Bridge, is a series of limestone shoals that form a rough connection between the northwest coast of Sri Lanka and Pamban Island, 30 miles away. The history of Rama Setu is intertwined with local legend. According to Hindu lore, it was built by an army of warrior monkeys known as “Vanara” to help the god Rama save his wife Sita from the Demon king Ravana. While this origin story is widely treated as myth rather than reality, there are those who assert that Adam’s Bridge was in fact built and was never a naturally occuring land bridge. All we know for sure is, back in the 15th century, it was entirely above sea-level and traversable.

#16: Macropinna Microstoma
Think that’s a weird name? Wait til you see the fish it belongs to! First discovered in 1939, this mysterious and thoroughly alien-looking creature wasn’t photographed alive until 2004. It spends its life at depths between 2,000 and 2,800 feet, and though it’s been caught a number of times over the years, its fragile anatomy has made it incredibly challenging to study. From the “barreleye” family, Macropinna microstoma has a translucent domed head, which, coupled with its unique tubular eyes, gives it an advantage over its prey. The tubular eyes are extremely well-suited for capturing light in its dark habitat, while its domed head allows it to not only look forward, but also up through its own head. Unique? Sure, but also super creepy-looking.

#15: Gulf of Khambhat Ruins
Discovered in the early 2000s, these alleged ruins are still generating controversy decades later. Located off the coast of Gujarat in the Gulf of Khambhat, this archeological site is seemingly made up of city-like structures and home to various artifacts. But because the area was dredged rather than being explored via more careful methods of excavation, the scientific community is divided as to the significance of the results. The structures are compelling, but the relevance of the carbon-dated materials from the site is hotly debated. If they are indeed the tools of an ancient settlement, dated at 9,500 years old, that would make the Gulf of Khambhat ruins the oldest known civilization.

#14: Australia’s Cannibal Shark
Just as lions rule the savannah, great white sharks rule the seas. Okay, technically, killer whales have been known to target them, but that’s not what happened here. Australian scientists were shocked and utterly perplexed when a 9-foot long great white shark was apparently devoured. It had been tagged with a tracker as part of a study, and when said tracker washed up on-shore, the data contained within showed a sudden spike in temperature followed by a staggering 1,900-foot dive. After careful investigation, the researchers were left with only one possible conclusion: it was eaten by a cannibal shark of the same species estimated to be 16 feet long and two tons! Terrifying, right?

#13: Baltic Sea Anomaly
In 2011, Swedish diving team “Ocean X” were searching for sunken treasure in the Gulf of Bothnia. They stumbled instead upon something far stranger. Using sonar equipment to take a rough image of the object, they reported that it was 200 feet in diameter and bore distinct design patterns that seemed unnatural. Adding to the mystery of the Baltic Sea Anomaly is the fact that, according to the team, there was electrical interference in the area, preventing them from getting a clearer image. The team has even suggested that it could be a UFO. Needless to say, scientists are skeptical. It doesn’t hurt though that the structure looks vaguely like the Millenium Falcon or Ebon Hawk from “Star Wars.”

#12: Light Wheels in the Persian Gulf
We’re starting to notice a pattern here. If you’re on the hunt for an oceanic mystery of your very own, explore a gulf! Sometimes poetically referred to as “ghosts of the ocean,” light wheels are large glowing circles of light that appear on the water and have been observed for decades; some reports actually go all the way back to the 18th century. Often measuring hundreds of feet in diameter, these eye-catching anomalies have been explained away (most notably by oceanographer Kurt Kalle) as the result of bioluminescent plankton and seismic waves. While plausible, such theories struggle to explain the variety of shapes that the light wheels take, or the fact that they appear to spin at varying speeds.

#11: The Milky Seas Effect
Sailors’ tall tales are often dismissed as mere superstition. Well, the Milky Seas Effect is one story that we can confirm – even if we don’t entirely understand it. Historically, sailors have reported seeing large sections of the sea become a pale milky white (or blue) and emit a faint glow. Now, thanks to modern technology, we know that the milky seas effect is not only real, but the result of bioluminescent bacteria. While that’s all well and good, we still can’t figure out what causes these sudden explosions in bacterial populations or the other variables that result in this unique sight.

#10: Leptocephalus Giganteus
Described by Anton Bruun in 1930 and Peter Henry John Castle in 1959, Leptocephalus Giganteus is an extremely rare species of eel thought by some to swim the ocean depths. Only two such specimens have ever been studied and they were in the larval state, meaning that they were nowhere close to reaching maturity. But even as a larva, one specimen was roughly 6 feet in length. And given that eel larva is typically 1/32nd of its adult length, that would suggest a truly monstrous eel come maturity. Now, contemporary scientists have suggested that Leptocephalus Giganteus was likely misidentified and would not not grow substantially beyond that point, but without further study, it’s impossible to say! Leptocephalus Giganteus could be the reality behind sea serpents.

#9: Aegean Sea Ruins
In 2015, researchers hailing from Greece and Sweden made one of the most remarkable archaeological discoveries of the 21st century. Working south of Athens in the Kiladha Bay, the team was exploring fertile territory; the area is rich in archaeological sites. But nothing could have prepared them for what they found. What began with a few pottery fragments led researchers to uncover the ruins of an entire lost city – one that occupied somewhere in the ballpark of 12 acres of land. The city dates back to the Bronze Age and was seemingly protected by a wall complete with defensive towers – structures unseen until now in any other ancient Greek sites. How this seemingly once-great city fell, however, is anyone’s guess.

#8: Colossal Squid
This terrifying deep sea beast was first discovered in 1925, and its existence admittedly lends a certain credibility to all those myths about sea monsters. Because colossal squids are so elusive, our knowledge of their anatomy is somewhat limited, but based on beaks that have been recovered, it’s been hypothesized that, at maturity, they could weigh up to 1,500 pounds and measure 30 to 33 feet in length. Only a handful of specimens have ever been found, which makes sense given that they generally inhabit the Antarctic Ocean and dwell at depths of up to 7,200 feet. As if the colossal squid’s size wasn’t intimidating enough, they’re armed with both swiveling and three-pointed hooks on their limbs.

#7: The Ruins of Dwarka
The lost city of Dwarka is one of the rare instances of a myth possibly being confirmed as fact. According to legend, the Hindu deity Krishna founded the now legendary city of Dwarka long ago. The city is sacred in the Hindu faith, and is said to have been unparalleled in its beauty and splendor – rich in greenery, wildlife, and palaces. It was utopia – that is until it was swallowed up by the sea. The Dwarka of legend has understandably long been dismissed as a work of fiction, but in the 1980s, with the discovery of underwater ruins off the coast of the modern day coastal town of Dwarka, people were forced to reconsider that assumption. The research continues to this day.

#6: The Bimini Road
Dubbed the “road to Atlantis,” the Bimini Road (or Bimini Wall, as some would argue) is a rock formation that runs for a half mile underwater in the Bahamas. Located near North Bimini Island, this mysterious marine landmark is made up of large, roughly rectangular limestone blocks which seem to form a road or wall-like pattern. Analysis of the stones, including carbon dating, has led researchers to conclude that the Bimini Road is a natural formation resulting from erosion and the currents. But… given that there are two other similar patterns in the area, and considering the fact that some of the stones appear to be stacked atop one another, there are some who maintain that there’s more to the Bimini Road than carbon dating suggests.

#5: The “Atlantis of Japan”
Various underwater ruins around the globe have been posited as the “lost city of Atlantis” upon their discovery. But if there’s one that leads the pack, it’s the Yonaguni Monument. As with the Bimini Road, many have dismissed these underwater rock formations as being naturally occuring. But the structure is oddly geometrical, and includes reliefs that vaguely resemble animal carvings, and what appears to be the remnants of columns. As such, there are some, like Professor Masaaki Kimura, who have argued in favor of this being the remnants of a lost civilization, possibly even the lost continent of Mu (another name for Atlantis).

#4: Bloop
The “Julia” recording certainly made waves in the scientific community, but if there’s one deep sea sound file that people never seem to get tired of debating, it’s the “Bloop.” And it’s not just scientists versus conspiracy theorists – not even researchers within relevant fields seem to be able to agree about its origins. This ultra-low-frequency, high amplitude sound was recorded in 1997. First, it was speculated that the sound was caused by icebergs dragging along the ocean floor. But then, in 2002, Christopher Fox of the National Oceanic and Atmospheric Administration speculated that it had been produced by an animal. Flash forward another 10 years and the NOAA was once again pointing towards ice quakes.

#3: The Megalodon
Human history, across various cultures, is chock full of myths and legends about sea monsters that tormented sailors of yesteryears. Unlike the Leviathan or the Kraken however, we know for a fact that the Megalodon once swam these seas. The word “megalodon” literally means “big tooth.” Measuring up to 59 feet in length and reaching upwards of 59 metric tons, these prehistoric terrors certainly earn the name. The general scientific consensus is that they went extinct millions of years ago, but there are those who believe that they continue to survive in secret. And it’s not just Discovery Channel fueling the speculation – species like the Coelacanth and megamouth shark remind us that anything could lurk in the ocean depths.

#2: The Lost Submarines of 1968
Life aboard a submarine isn’t for the faint of heart. You’re literally trapped in a long metallic cylinder hundreds of feet below the surface of the ocean. When something goes wrong... it often goes very wrong. Despite the inherent risks however, four such vessels going missing in quick succession makes for an incredible coincidence. With 318 lives and four subs lost in a single calendar year, 1968 is the most deadly year in submarine history since the end of WWII. The USS Scorpion, the INS Dakar, the Minerve, and the K-129, hailing from the States, Israel, France, and the Soviet Union respectively, all disappeared under mysterious circumstances and continue to be the subject of speculation decades later.

#1: Bermuda Triangle
Roughly defined by Puerto Rico, Miami and the island of Bermuda, this triangle is the subject of much superstition. For the record, this is among the most heavily traveled stretches of ocean in the world, and most trips are completed without incident. But... the accidents and disappearances that have transpired are notably strange. The Ellen Austin incident allegedly saw not one, but two crews disappear from a derelict ship found in the triangle. The USS Cyclops was a US Navy ship that disappeared with all 309 sailors. There are countless such stories, leaving an enduring shroud of mystery over these stormy seas.

Which deep sea mystery do you find the most intriguing? Let us know in the comments below.