You won’t believe what authorities have discovered deep underwater.

About 71% of Earth is covered in water. The deepest, darkest part of the ocean is a staggering 36,070 feet (10,994 meters) below sea level. Scientists are constantly discovering new things in the mysterious abysses of our planet’s expansive oceans. However, there are some things that have been discovered in the briny deep that science can’t even begin to explain.

10. The Baltic Sea Anomaly

In 2011, a Swedish diving team went on an excursion to the Baltic Sea to search for shipwrecks. When the team returned from the trip, they brought a sonar image that quickly became one of the creepiest things found underwater.

In this image of a 197-foot (60-meter) section of the sea floor, the divers identified features such as stairways and ramps that were likely man made. When they attempted to get a clearer image the following year, they were unable to do so because of “mysterious electrical interference.”

No one was able to present a reasonable explanation of the structure depicted in the image. The peculiar shape reminded many of a UFO, some even comparing it to the Millenium Falcon from Star Wars. This led to speculation that the Baltic Sea Anomaly was an alien craft that had crash-landed on the floor of the Baltic Sea, possibly part of a larger fleet of extraterrestrial spaceships.

9. New Jersey’s Train Graveyard

It isn’t unusual for railroad companies to discard locomotives when newer technologies make them obsolete. However, when you decide to jettison them to the bottom of the ocean, you create one of the creepiest things found underwater.

In 2013, archeologists discovered several 1850s-style trains on the sea floor just off the coast of New Jersey. The locomotives were remarkably well-preserved, leading the discoverers to wonder just how long they had been at the bottom of the ocean.

This is where the case becomes even more baffling: the archeologists who discovered the trains were unable to find any records of the trains being lost. Even more surprising was the researchers couldn’t even find records of the trains being built.

Where did these trains come from, and how did they get to the bottom of the ocean? Experts still can’t answer these questions.

8. Lake Michigan Stonehenge

Everyone has heard of Stonehenge, the popular Druid monument in England. However, did you know that explorers have found a similar stone monument deep underwater?

Explorers searching for sunken ships in Lake Michigan in 2007 came across the bizarre structures. They appear to be around 9,000 years old, which would make them about as old as Stonehenge. However, one of the structures has a carving that depicts a Mastodon, a creature that went extinct over 10,000 years ago.

How would an ancient civilization, with limited technology, have been aware of such a bygone creature? The time discrepancy has led some to theorize that the structures formed an ancient base for aliens visiting Earth who had been observing the planet long enough to be aware of extinct creatures.

7. Bimini Road

The Bimini Road is a half-mile (.8 kilometer) rock formation underwater near the Bahamas. It is made up of limestone blocks. The rocks have straight lines that could only have been cut by humans, leading many to speculate about how and why the road was created.

There are several popular theories about Bimini Road. Some speculate that the road is an important clue to the location of the legendary lost city of Atlantis. Proponents of this theory argue that the Bimini Road was once a highway leading the the mythical city.

Some question how the road could have led to Atlantis if no other ruins were found nearby. Proponents of the Atlantis theory believe that the ancient metropolis was completely pulverized by aliens that attacked Earth, leaving Atlantis as nothing but a heap of rubble. Some believe Bimini Road is the only part of the city that the aliens left untouched.

6. The Belize Blue Hole

The Belize Blue Hole, sometimes called the Great Blue Hole, is a popular spot for divers. It is famous for being the largest sea-hole in the world with a diameter of 984 feet (300 meters) and can even be seen from space.

While this sea-hole appears to be natural, it’s perfectly circular shape has led many to speculate about its origins. Some claim that something so geometrically perfect is an anomaly that could have only been created by aliens.

Some divers who have visited the Belize Blue Hole call it one of the creepiest things found underwater. They report seeing unusual things while diving into the chasm, leading some to believe that the Blue Hole is home to mermaids or even sea monsters.

5. The Sea of Galilee Monument

Despite its name, the Sea of Galilee is actually the lowest freshwater lake on Earth. Yet, it is home to one of the creepiest discoveries found underwater.

In 2003, researchers found a cone-shaped structure in the lake’s waters when performing a sonar scan. After studying it, the researchers were unable to determine its age, how it was made, or what it might have been used for. The researchers were particularly astounded to find that part of it was made from huge boulders that could only have been sourced from at least a mile away. How would the ancient people who created it have transported the huge rocks?

The discovery of the structure has led to significant controversy. Some claim that it was created to allow Jesus to fake his miraculous walk on water, outraging many Christians. However, this doesn’t answer the question of how such a huge structure was created. Scientists still have no explanation for this eerie underwater edifice.

4. The Yonaguni Monument

The Yonaguni Monument is another of the bizarre things found underwater to cause significant controversy. While some assert that it is a natural formation, others insist that the regular lines and sharp angles could only have been man made.

The structure is in the shape of a tiered pyramid, leading many to refer to it as Japan’s Atlantis. Some speculate that it could have been used as a temple or stadium. However, others claim that ancient peoples would have lacked the tools necessary to assemble the structure and that the true answer lies with extraterrestrials.

Proponents of this theory assert that the monument contains alien technology and that it was left behind for a specific purpose. Perhaps it is a device that could allow us to communicate with its alien creators; however, some speculate that it might also contain a mechanism intended to destroy the human race. We have no way of knowing this mysterious monument’s true purpose.

3. The Antikythera Mechanism

The Antikythera mechanism is an analog computer likely used by the ancient Greeks to predict astrological events. It is a complex piece of machinery with 37 gears that allowed it to track astrological positions. It was discovered in 1900 by a group of divers exploring the Antikythera shipwreck.

There are many bizarre theories about this device. Some claim that the technology was far too advanced to have been created by the ancient Greeks and that it must have been given to them by aliens or a time traveler, or that it had been scavenged by an explorer who secretly discovered the lost city of Atlantis. Some also theorize that it was created by the Illuminati or a race of lizard-people as a hoax to fool the rest of the world. These extraordinary theories certainly earn the mechanism a place among the creepiest things found underwater.

2. Entrance to Xibalba

In 2018, a diver exploring off the coast of Mexico, near the Yucatan Peninsula, swam through a narrow tunnel. Little did he know that he was about to make an important archeological discovery.

The ancient Mayans who lived on the peninsula believed that one way to enter the underworld was through underground caves. Researchers have long sought the location of these caves, but have come up empty-handed. However, many believe that the tunnel this diver discovered may be the entrance to the Mayan underworld of Xibalba. Based on its location, this tunnel may lead to an underground cavern where it is believed that Mayans performed human sacrifices to appease the gods of death.

According to Mayan beliefs, this tunnel would have been a passageway connecting the world of the living to the world of the dead. The tunnel itself may be unremarkable, but the thought of being deep underwater, in the dark depths of the ocean, traveling into the mysterious Mayan underworld makes it an eerie discovery.

1. The Skeleton Lake of the Himalayas

You wouldn’t expect one of the creepiest things found underwater to reside in the lofty heights of the Himalayas. Its remote location is only one reason this spot is one of the eeriest underwater discoveries in history.

Roopkund Lake is a shallow lake that is 16,499 feet (5,209 meters) above sea level. In 1942, a British ranger surveying the lake made a horrifying discovery: thousands of bones were submerged in the lake, floating in the water, and strewn on the shore. Authorities later estimated that between 200 and 300 human skeletons were interred in the lake.

The lake is so far from any known human civilization that researchers were puzzled: how could the remains have ended up in this remote body of water? Even more surprising was that testing determined that all of the deceased had died at around the same time, but were made up of two distinct groups completely unrelated to each other. Who were these unidentified peoples, and how did they die?

Theories have abounded, but no one has been able to conclusively solve the mystery of Skeleton Lake.