The Ocean’s Biggest Mysteries: What Are They Hiding From Us?

Every day, we learn something new about the world. Some new facts to solve a centuries-old mystery or a new theory that suddenly makes an ‘impossible’ occurrence look very plausible. And while we’ve come to learn a lot about life on land, the terrifying reality that we know less – much less – about the vast oceans remains.

If you’ve got an eye for solving mysteries, you’re probably amazed by some of the world’s biggest secrets our oceans have to offer. From the unknown origins of seemingly man-made underwater structures to the undiscovered species of the deep sea, you might even be tempted to beat the scientists to it and figure out the truth behind the unexplained events. If you’re interested, bear with us and keep on reading!

In this post, we will introduce you to the top ten mysteries of the ocean as ranked by voters. The respondents were asked to upvote mysteries they would like to see resolved and the rankings were produced accordingly. From the deepest points in the ocean to the baffling events that took place on the surface, let’s take a closer look at some of the most intriguing mysteries of the ocean!

What Happened to the Crew of Mary Celeste?

Sailing brigantine, front view
Image Credit: Shutterstock / Mert Kahraman

In December 1872, Mary Celeste, an American-registered merchant brigantine was found sailing unmanned off the Azorean islands. As the crew’s disappearance came under investigation, it was revealed that the ship’s lifeboat was missing. Deeping the mystery is the fact that they abandoned personal belongings along with 6 months’ worth of supplies and valuable cargo including 1,701 barrels of industrial alcohol.

Since the investigation confirmed no foul play was involved due to a lack of evidence of any physical altercations, theories that the ship was raided were dismissed. When the vessel was found by Captain David Morehouse, Mary Celeste had a small amount of water in the hull. While one pump was disassembled, the other was in a working condition. One of the most plausible theories suggests that the captain of Mary Celeste and his crew abandoned the ship and tried themselves on rough waters after panicking when the hull started taking on water. This is backed by the fact that the captain noted risky sailing conditions in his last log entry.

What Lurks in the Deep Waters of the Mariana Trench?

Viewof the Mariana Trench, the deepest depths in the Western Pacific.
Image Credit: Shutterstock / DOERS

The bottom of the Mariana Trench is the deepest observed point in the ocean. It lies at a depth of 35,876 feet, making it one of the places hardest for humans to access due to the pressure there being 1,071 times higher than the standard atmospheric pressure at sea level. The trench itself is 1,500 miles long and some 43 miles wide.

The deepest point of the trench is the Challenger Deep where humans have only been two times – once in the 1960s and once in 2012 when Hollywood director James Cameron risked his life to dive into the eternal darkness. Needless to say, much about the Mariana Trench remains a mystery. One thing is sure, though. Even in the depths of the trench, life exists in the form of species that evolved to survive skyrocketing pressures. Who knows what else is down there?

How Was the Yonaguni Monument Made?

Technical scuba diver exploring underwater cenote.
Image Credit: Shutterstock /

The Yonaguni Monument is a submerged rock formation located off the coast of Yonaguni in Japan. Since its discovery in the late 1980s, scientists have been arguing about its origins and coming up with contradicting theories regarding their creation.

Also known as Japan’s Atlantis, the ruins consist of underwater pyramids, arched entrances, and narrow passages that must have been created by a skilled hand. But were they really? While some theories say the formations are man-made monoliths created by ancient civilizations predating modern humans, most agree that the structures were naturally shaped by the weathering and erosional processes affecting the large rock mass they are attached to.

Why Can We Only See Less Than 1% of Plastics Dumped Into the Ocean?

Plastic Pollution In Ocean - Turtle Eat Plastic Bag - Environmental Problem
Image Credit: Shutterstock / Romolo Tavani

The world is responsible for producing some 350 million tons of plastic waste each year with around 0.5% of this number ending up in our oceans. The majority of this plastic ends up in one of the five major gyres causing massive garbage patches such as the Great Pacific Garbage Patch that threaten the ecosystems.

Despite these massive numbers, less than 1% of plastics dumped into the ocean can be seen floating on the surface, meaning that the other 99% hides under the surface. While some of it floats deep under the ocean surface due to higher density, the majority of plastic breaks down into tiny pieces known as microplastics. These have already infiltrated the marine food chain and can be found in almost everything we eat. The real mystery hides not in the form or location of these microplastics but in finding out how ongoing pollution will affect us in the long term and what we can do to remove the particles.

What’s Hiding in the Unexplored Parts of the Ocean?

Underwater diver in deep sea dive
Image Credit: Shutterstock / Lillac

According to modern estimations, around 95% of the ocean has never been explored, mapped, or seen by humans. Not to mention that over 90% of ocean species have yet to be discovered. Who really knows what hides in the depths of the ocean and the deepest parts of our planet?

While reaching the ocean floor sounds like a big achievement, this is not the least explored part of our oceans. On the contrary, the majority of exploration needs to be done in the pelagic area of the ocean – the portion above the ocean bed and beneath the level reached by sunlight. As technology advances, we might figure out ways to cover more areas. Until then, we’re left to wonder if the megalodon really went extinct some 3.6 million years ago.

Giant Squid or Real-Life Kraken?

Flight of giant octopus underwater
Image Credit: Shutterstock / Kondratuk Aleksei

This one sounds like the title of a low-budget horror movie, but let’s go with the idea for a second. Giant squids are rarely observed in action thanks to their elusive nature. While their carcasses sometimes get washed up the shore, they are rarely seen alive and it wasn’t until 2006 that a 24-foot squid was caught on camera. Since then, his 43-foot-long cousin was also discovered.

While this may seem like a big deal, literally, squids roaming the depths of the ocean likely get even larger. Some scientists estimate that giant squids may grow up to 66 feet long. It is believed that these gigantic creatures inspired the creation of the legendary sea monster known as the Kraken.

How to Explain the Four Submarine Disappearances in 1968?

Naval submarine on open sea surface with cloudy sky
Image Credit: Shutterstock / noraismail

With the Cold War raging on in 1968, many things happened unexpectedly. And some of these events still aren’t solved up to this day. As tensions between world superpowers ran high, four submarines disappeared in less than one year.

The first vessel to go missing was Israel’s INS Dakar on January 25. The wreckage was discovered in 1991 but investigation revealed no certain causes for the disaster. Next was France’s Minerve which wasn’t found until 2019 with its hull divided into three portions. Shortly after, the Soviet Union’s K-129 submarine went missing without much explanation somewhere in the Pacific. In May of the same year, the United States’ nuclear vessel Scorpion also went missing while on a surveillance mission. To this day, it remains unclear what happened to the four submarines.

Who’s After Shipwrecks and Why?

A scuba diver with a torch explores a sunken shipwreck at the seabed of the Maldives islands, Indian Ocean
Image Credit: Shutterstock / Sven Hansche

Shipwrecks, including the remains of World War II vessels, are continuously disappearing in the Java Sea surrounding Malaysia, Singapore, and Indonesia. While the governments aren’t sure who’s behind their disappearances, it is clear they are being plundered. It is unclear, however, why anyone would bother stealing from the wrecks.

One theory suggests that plunderers are recovering pre-nuclear age steel from the vessels’ hulls or looting brass and aluminum left behind when the ships sank. Others, however, argue that such salvage operations are expensive and that the payoff would hardly cover the costs. While the investigation into these events continues, we’re left to ponder what the raiders are really after.

The Island of Bermeja – Real or Faux?

Old Map Gulf of Mexico
Image Credit: Shutterstock / yoshi0511

Bermeja was an alleged island off the coast of Mexico’s Yucatan Peninsula that appeared on world maps for over two hundred years until its last appearance in a 1921 atlas. The mystery? The island is nowhere to be found and it is still unknown to this day if it ever even existed.

As part of a USA – Mexico treaty on how to divide international waters in 1997, Mexico was promised to gain rights to the waters surrounding Bermeja provided they could locate the island. Bermeja was never found, leading to theories revolving around its existence. While some researchers theorized the island never existed and merely served as a ploy to confuse Mexico’s enemies, others say it is real but wrongly mapped. Some theories even go as far as accusing the US government of destroying the island to gain a claim to the region rich in oil.

The Oarfish – Natural Earthquake Detectors?

A seismograph that records the seismic activity of an earthquake.
Image Credit: Shutterstock / menur

Serpent-like sea creatures known as oarfish live deep under the surface of the ocean and can grow up to 56 feet long and weigh up to 600 pounds. Their intimidating size and appearance, however, aren’t what baffles humans the most. Oarfish, also known as the kings of herrings, have long been believed to be able to predict earthquakes and swim to the surface when danger is imminent.

While modern research papers on the legend of the oarfish dismissed the alleged connection between earthquakes and the ocean species, some people still believe oarfish are harbingers of disaster. This idea was once again reinforced in 2011 when a 9.0 undersea earthquake in the Pacific Ocean caused a tsunami that killed nearly 20,000 people in Japan. According to some reports, at least 12 oarfish were spotted near beaches in the moments leading to the megathrust earthquake. Maybe scientists don’t know everything there is to this myth?

Author: Zan Kokalj


Zan Kokalj is a veteran content writer, copywriter, and author inspired by the impact of ink on paper.

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