Top 10 Creepiest Deep Sea Mysteries

Script written by Michael Wynands. There are too many unexplained deep-sea mysteries: does the colossal squid exist? What is the Baltic Sea Anomaly? Is the Cuban underwater city the lost city of Atlantis? Are there still living megalodons? WatchMojo counts down ten of the creepiest deep-sea mysteries that will freak you out. Special thanks to our user Christo, Leo Lazar Jakšić, MikeMJPMUNCH, ViolaCello, Abomb53 and Jaime Enrique Gutierrez Pérez for suggesting this idea! Check out the voting page at http://WatchMojo.comsuggest/Top%20Ten%20Ocean%20Mysteries

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Script written by Michael Wynands.

Top 10 Unsolved Deep Sea Mysteries

Space may be the final frontier, but we still have plenty to figure out right here on planet Earth. Welcome to, and today we’re counting down our picks for the Top 10 Deep Sea Mysteries.

For this list, we’re only interested in underwater mysteries, not mysterious events or phenomena that take place on the surface of the deep blue.

#10: Gulf of Mexico Shipwreck

There may be more than 2000 known shipwrecks scattered across the seabed in the Gulf of Mexico, but few have captured the attention of both the public and scientists like this vessel. Estimated to be 200 years old, and hidden away below some 2600 feet of water, this ship has been the subject of one of the most elaborate and challenging underwater archeological expeditions in history. It was discovered by chance during the laying of an Exxon Mobil pipeline, and multiple underwater rovers have been sent down to gather information, but every attempt has consistently suffered from unlikely technical failures, leading some to believe that the ship is cursed, and meant to remain a mystery.

#9: Colossal Squid

The kraken might be a mythical creature, but the colossal squid is big, elusive and scary enough to work as a stand-in. To put the colossal squid in perspective, let’s consider the slightly smaller giant squid. First caught on film in 2012, the giant squid has been known to measure up to 43 feet long and weigh an estimated 1000 pounds. The colossal squid on the other hand, reaches up to 46 feet long and a whopping 1650 pounds. While the giant squid’s tentacles feature suckers with teeth on them, the colossal squid boasts a number of sharp hooks. Only one mature living specimen has ever been caught and studied, leaving us with many unanswered questions about this deep-sea monster.

#8: Leptocephalus Giganteus

What’s longer: The body of the elusive Giant Leptocephalus, or the name of the man who first described it, Peter Henry John Castle? The specimen, caught by Castle off the coast of New Zealand in 1959, measured roughly 35 inches in length. But its anatomy was consistent with the larval stage of the species, suggesting that, in “eel terms,” it was just a baby. Considering that leptocephali are typically 2 to 4 inches in length, Castle’s discovery certainly sparked controversy. Based on his calculations, an adult leptocephalus could grow into a 98-foot long eel once it fully matures. Other examples of L. Giganteus have been reported, but no one has come across a mature specimen to confirm Castle’s theory.

#7: Aegean Sea Ruins

As one of the world’s oldest civilizations, Greece certainly has its fair share of historical sites. But the Aegean Sea Ruins present one of the most noteworthy discoveries in recent Greek history. Found off the coast of Delos in 2014, what first appeared to be the remains of a port was later discovered to be a pottery workshop, complete with kiln and various pots, a retaining wall, pathways, towers, and other unidentified buildings covering nearly 12 acres of seabed. Greek media outlets have dubbed it an “underwater Pompeii.” The failed coastal settlement is estimated to have succumbed to the sea some 4500 years ago. Researchers suspect it may be the ancient city of Kane, where the Athenians defeated the Spartans.

#6: Cuban Underwater City

The discovery of an ancient underwater city is always cause for excitement. But when that city sits beneath one of the most mysterious geographical locations on earth, the Bermuda Triangle, wild theories abound. In 2001, sonar scans off the coast of Cuba revealed a series of distinctly geometric structures. Considering the structures sit at a depth of 2000 to 2460 feet under water, it’s hard to fathom how or when they would have been constructed. Some experts have gone so far as to say they can identify pyramids and even a sphinx. Other theories have called it the lost of city of Atlantis. Curiously, there’s been a distinct lack of follow-up research, which has many conspiracy theorists yelling “cover up!”

#5: Baltic Sea Anomaly

There’s estimated to be over 100,000 ship wrecks sitting at the bottom of the Baltic Sea – and they may not all be from this planet. Known by some as the Baltic UFO, this anomaly was discovered by “Ocean X Team,” a group of Swedish divers. The structure, roughly 200 feet in diameter, has prompted numerous theories as to just what it could be: a spaceship, an anti-submarine device, or simply a geological formation. But the distinct shape of the structure, which bears an uncanny resemblance to the Millennium Falcon, coupled with the fact that electronic devices seem to stop functioning when near it, keeps people questioning its origins.

#4: The Milky Sea Effect

We may have the technology to understand the “how” of this mystery, but scientists are still scratching their heads as to the “why.” For centuries, sailors have described crossing mysterious milky glowing patches of sea. Seafarers are known to be a superstitious lot, so little stock was put into these tales until 1985, when a research team managed to take samples of the milky seawater. They identified the cause as bacterial in nature, finally giving this seafaring story legs to stand on. While subsequent studies and satellite imaging have given us a better understanding of this bioluminescent phenomenon (which can cover an area the size of Connecticut), we have yet to understand why the bacteria suddenly congregate in this manner.

#3: Surviving Megalodons

According to Wikipedia, the megalodon is officially extinct. Most scientific sources agree with that position. But thanks to the Discovery Channel’s “Megalodon - The Monster Shark Lives” which was marketed as a dramatized documentary, there is renewed interest in the possible continued existence of this fierce predator. It’s estimated at a maximum of 59 feet long, three times larger than the biggest great white shark. The coelacanth fish was thought dead for 65 million years before its rediscovery in 1932, and the 15 foot long megamouth shark was unknown until 1972, so maybe the Megalodon is still around. There have been countless eyewitness reports of sharks in excess of 50 feet in length, which also helps keep this myth alive.

#2: The Bimini Road

Multiple underwater ruins have claimed the title of the “real” lost city of Atlantis, but few inspire enthusiasm like this large arrangement of stones in the Bahamas. Although some have dubbed it “the road to Atlantis,” it’s more often called the Bimini road, due to its location beneath the water near North Bimini Island. Later expeditions suggest that “the Bimini wall” may be more appropriate. Running a half mile long, and made of sandstone blocks, it is one of three similar patterns of rock formations in the area. Whether it’s a road or an ancient wall, no one can quite figure out how the stones were engineered to create such a captivating and perplexing sight.

Before we unveil our top pick, here are a few honorable mentions.
- Macropinna Microstoma
- Gulf of Khambat Ruins
- Australian Cannibal Shark

#1: “Atlantis” of Japan

Two thousand years ago, a city sunk into the ocean off the coast of Yonaguni Jima following massive seismic activity - or so the story goes. As is the case with many underwater discoveries, the Yonaguni monument and its surrounding structures have been dismissed by some as a rock formation naturally shaped by erosion. However, the structures are distinct in their sharp angles, animal-like shapes and apparent columns, leading many to side with the “ancient civilization” argument. The most difficult structure to defend as having been naturally formed is a stepped pyramid that stands at 25 meters in height. According to a local marine geologist, Masaaki Kimura, this may be Mu, one of several lost continents theorized throughout the ages.

Do you agree with our list? What deep sea mystery do you find to be the most interesting? For more elusive top 10s published every day, be sure to subscribe to

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