38 Unexpected Things the Ocean Served Up

It’s kind of wild when you think about it, our planet is mostly covered in water, yet we’ve barely scratched the surface of what’s actually down there. The ocean makes up more than two-thirds of Earth’s surface, but it’s still one of the least explored places we know.

For all our satellites, submarines, and deep-sea robots, most of the underwater world remains a mystery. That means there’s a whole universe of strange creatures, eerie sounds, and unexplained phenomena waiting to be uncovered. And every new discovery reminds us that the ocean still holds secrets we can’t even begin to imagine.

According to NOAA Ocean, as of June 2025, only about 27.3% of the world’s seafloor has been mapped. That might sound like progress, but it also means that more than 70% of what lies beneath is still a mystery. Part of the problem is how vast and deep the ocean really is.

Around 90% of it qualifies as “deep ocean,” that’s anything below 200 meters, or roughly 656 feet. Down there, sunlight can’t reach, pressure crushes anything unprepared, and it’s pitch black. Even with advanced sonar and autonomous submersibles, exploring those depths is a slow and expensive process.

We dove deep into the digital depths to find some of the most mind-bending, unsolved ocean mysteries that continue to stump scientists and explorers alike. From mysterious sounds echoing through the abyss to lost cities that may or may not exist, these stories prove that the ocean still has plenty of surprises left for us.

So buckle up and get ready to plunge into the unknown - because down there, reality is often stranger than fiction.

The Stronsay Beast

In 1808, after a storm, the body of a massive, unknown creature washed ashore on the island of Stronsay in the Orkney Islands. locals measured it and said it was 55 feet long, not counting the missing tail.

Naturalists couldn’t identify it, but later experts thought it might have been part of a giant shark. witnesses described it as having three pairs of limbs, ribs lined with bristles, and a “mane” of glowing bristles running along its back. Its stomach contents were red.

The creature’s description reminded some of later reports about the Loch Ness monster, but its cartilaginous skeleton suggests it was most likely a shark, not an unknown sea creature.

Sydney Moore

The Giant Shark

In November 2003, a tagged female great white shark suddenly vanished. Data from her tag showed a dive to 1,903 feet, and the temperature jumped from 46°f to 78°f, suggesting a sudden attack. Scientists believe she was eaten by a larger, more aggressive shark

Berthold Grünhagen

Kaz II, Dubbed "The Ghost Yacht"

In April 2007, the yacht Kaz II was found drifting near the Great Barrier Reef off Australia’s coast. Everything on board looked normal, but the three crew members were gone. Some say they drowned trying to save one another or were taken by another vessel, but no bodies were ever found.

Ian Hitchcock

Baltic Sea Anomaly

In 2011, while exploring the Baltic Sea floor, the Ocean X team, a company known for deep-sea exploration and searching for lost treasures, discovered a strange 200-foot-wide object that looked like the Millennium Falcon from Star Wars.

Even stranger, their communication systems stopped working when they were right above it, but worked fine a few hundred feet away. Scientists who examined soil samples said the object was natural, yet the interference remains unexplained.

Hauke Vagt, Brooke Morton

The HMS Daedalus' Sea Serpent

In 1848, HMS Daedalus was off the coast of present-day Namibia on its way to Saint Helena when Captain McQuhae and his crew spotted what they described as a sea serpent.

Captain McQuhae said the creature passed close enough that he could’ve recognized its face if it were a man he knew. eyewitnesses claimed it was about 60 feet long and moved at 12 to 15 miles per hour. Today, some believe they actually saw a sei whale, though no one can say for sure.

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Deep Sea Hydrothermal Vents

In 1977, scientists exploring east of the Galapagos Islands with the submersible Alvin discovered the first deep-sea hydrothermal vents. These chimney-like structures release mineral-rich water reaching about 750°f.

Today, researchers know these vents are home to unique life forms that thrive without sunlight, and studies suggest that Earth’s earliest ancestor may have lived near one around 3.8 billion years ago.

P. Rona / OAR/National Undersea Research Program (NURP); NOAA

The Yonaguni Monument

In 1986, Kihachiro Aratake, a diving enthusiast and director of the Yonaguni-Cho Tourism Association, spotted a massive underwater formation off Yonaguni Island in Japan. The structure, shaped like a step pyramid, was surrounded by shapes resembling ruins.

Over the years, scientists and explorers have debated its origin. Some say it’s just natural sandstone that fractured neatly over time. Others believe it’s the remains of an ancient civilization, possibly one that existed when the area was still above sea level around 10,000 years ago.

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The Sarah Joe Mystery

In February 1979, five Hawaiian fishermen set sail on a small boat called the Sarah Joe. When a storm hit, they failed to return, and the boat disappeared.

Nine years later, in 1988, wreckage from the Sarah Joe was found on an uninhabited atoll 2,000 miles away. Nearby, there was a grave containing the remains of one fisherman, Scott Moorman.

How the boat traveled so far, what happened during those years, and the fate of the other four men remain a mystery.

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Mysterious Ocean Sounds

In 1960, scientists picked up strange underwater sounds in the Southern Ocean near Antarctica; they sounded like a giant duck quacking, earning the name “Bio-Duck.”

For decades, experts couldn’t figure out what caused them. Now, they believe Antarctic minke whales are behind the noises, as their songs closely match the “Bio-Duck” sound.

Still, the mystery isn’t fully solved; these quacking sounds sometimes appear in places where minke whales don’t live. Scientists are still investigating.

Sergio Kian

Submarine Disappearances In 1968

1968 was a tragic year for submariners. Within six months, four submarines - USS Scorpion, Soviet K-129, French Minerve, and Israeli INS Dakar were lost, killing 318 people. Each disaster had its own story, and many details remain unexplained.

imaginima

The Kraken

For centuries, sailors in the North Atlantic told chilling tales of the Kraken, a massive, bloodthirsty sea monster said to drag ships to the depths. Today, we know these legends likely came from sightings of giant squids, creatures as big as old sailing ships but harmless to humans. The Kraken remains a mysterious legend born from the sea.

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The Loneliest Whale In The World?

For centuries, sailors in the North Atlantic told chilling tales of the Kraken, a massive, bloodthirsty sea monster said to drag ships to the depths.

Today, we know these legends likely came from sightings of giant squids, creatures as big as old sailing ships but harmless to humans. The Kraken remains a mysterious legend born from the sea.

Andrea Holien / pexels (not the actual photo)

El Dorado Of The Seas

In 1641, the English galleon Merchant Royal sank off the coast of Cornwall while carrying gold and silver back to England. Captain John Limbrey had also loaded treasure from another damaged ship in Cadiz.

Greed proved fatal; the vessel leaked and sank, taking its crew and cargo with it. The “El Dorado of the Seas” has never been found, though searches still continue.

Andreea Swank

Mystery Of Giant Ice Circles

Astronauts have occasionally spotted large, mysterious circles on the ice of Siberia’s Lake Baikal, seen in 1986 and 1994. Some claimed aliens made them, but scientists say they’re caused by methane gas heating the water, which swirls from Earth’s rotation and leaves these giant circular marks.

ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center.

The Disappearance Of The SS Naronic

The SS Naronic, a White Star Line ship—the same company behind the Titanic set sail from Liverpool to New York on February 11, 1893, and vanished with 74 people aboard.

Later, bottles were found containing supposed messages from the crew claiming they’d hit an iceberg, and two lifeboats were discovered near the same area where the Titanic would sink years later. But the letters turned out to be fake, and the Naronic’s fate remains a mystery.

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The Mystery Of Fishing Boat "Fausto"

In 1968, the fishing boat Fausto left La Palma with three crewmen and one passenger. Four days later, a British ship found it drifting far from land. Though weak and exhausted, the men refused help, choosing to continue alone.

Four months later, the Fausto resurfaced empty except for the mummified body of passenger Julio García. The missing crew and the torn pages of García’s diary remain an unsolved mystery.

forums.spacebattles.com

Flannan Isle Mystery

In 1900, a relief crew reached the Flannan Isles Lighthouse in Scotland and found all three keepers missing. The light had been off for days, and everything inside looked suddenly abandoned: beds unmade, coats still hanging. Officials claimed they were swept away by a storm, but the truth remains a mystery.

Paulius Dragunas

Mary Celeste

In 1872, the ship Mary Celeste was found drifting in the Atlantic with its cargo and belongings untouched, but the crew, captain, his wife, and their daughter had vanished. Theories range from pirates to mutiny, but the real cause remains unknown.

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Vastly Under-Explored Deep Ocean

The ocean covers about 70% of Earth’s surface, yet we’ve only explored roughly 20% of it. The rest remains a vast, mysterious world still waiting to be discovered.

Ant Rozetsky

Asia’s Disappearing WWII Shipwrecks

The Guardian recently reported that around 40 World War II submarines in the Pacific Ocean were taken apart by divers for personal use. These wrecks may have contained up to 4,500 crew members’ remains.

Leonardo Lamas

Mysterious Purple Blob On The Ocean Floor

Scientists aboard the E/V Nautilus found a strange purple blob on the seafloor. After retrieving it, they suggested it might be a new type of nudibranch a shell-less sea slug that crawls along the ocean floor looking for food. It definitely looks odd!

Brian Clark Howard

The Island Of Bermeja

Bermeja was a supposed island off Mexico’s Yucatán Peninsula, shown on maps since the 1500s but later found to be missing. Some believe it sank due to rising sea levels, while others suspect it was destroyed to alter oil zone borders. Divers claim to have found traces underwater, though no full study has confirmed it.

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The Upsweep

“The Upsweep” is a mysterious underwater sound first recorded in 1991 by NOAA’s Pacific monitoring system. It’s a series of rising tones that repeat every few seconds and can be heard across the Pacific Ocean. Once thought to be biological, that idea was ruled out in 1996.

The source lies somewhere between New Zealand and South America, and while scientists now suspect volcanic activity, no one knows for sure. The sound has faded over time but remains detectable.

pmel.noaa.gov

Giant Oarfish

The oarfish is a deep-sea creature rarely seen by humans. It can grow up to 30 feet long, and many believe ancient sea-serpent legends originated in oarfish sightings. Sometimes they wash ashore before big storms, earning them a reputation as omens of disaster, as before Japan’s 2011 earthquake and tsunami.

Wm. Leo Smith

Mystery Of The M. V. Joyita

In 1955, the former yacht M.V. Joyita, once owned by film director Roland West and named after his wife, actress Jewel Carmen, was found drifting half-submerged in the Pacific. It had been traveling from Tokelau to Samoa but never arrived; its 25 passengers and crew vanished without a trace.

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Mysterious Disappearance Of Ghost Ship Carroll A. Deering’s Crew

In January 1921, the schooner Carroll A. Deering vanished while sailing from Barbados to Norfolk, Virginia. It was later discovered off North Carolina’s coast, cargo and belongings untouched, but the entire 12-person crew gone without a trace.

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The Disappearance Of The SS Waratah

The SS Waratah, a cargo-passenger liner sailing from Australia to London, vanished in 1909 between Cape Town and Durban with 211 people on board. Despite an extensive search, no trace was found, only bits of debris that might have belonged to the ship.

It’s believed the Waratah was caught in a powerful storm, capsized, and sank. Some passengers had noticed the vessel leaning to one side; one, engineer Claude Sawyer, even left the ship early, unknowingly saving his life.

Later, a man claimed he saw a steamship swallowed by a huge wave that day, though it was never confirmed. Curiously, eight other ships named Waratah have since sunk—but one, the steam tug ST Waratah built in 1902, still operates in an Australian port.

Unknown author

A UFO Crashed Off The Coast Of Shag Harbour, Nova Scotia

On October 4, 1967, eleven people in Shag Harbor, Nova Scotia, reported seeing a glowing object crash into the Gulf of Maine.

Police launched a large rescue search, but no wreckage was ever found. The story made headlines across Canada before fading away, though rumors later claimed that Canadian and U.S. military teams secretly investigated the site.

NLPEI

The Sinking Of MV Derbyshire

In 1980, the British bulk carrier MV Derbyshire sank during a typhoon near Japan, killing all 44 crew members. Fourteen years later, investigators found the wreck and discovered that waves had torn off small ventilation covers, letting water flood the ship. When powerful waves hit again, the pressure blew open the cargo hatches, causing the vessel to sink within minutes

PA Images / Getty Image

Bioluminescent Waves And “Milky Seas”

Since ancient times, sailors have spoken of the mysterious “Milky Sea,” a strange green glow that lights up the ocean at night. Scientists later discovered it’s caused by bioluminescent bacteria, with its appearance tied to climate patterns like El Niño. Research continues to uncover what this glow reveals about ocean life.

Wanmei Liang, Story by Adam Voiland.

The Devil’s Sea

The Pacific Ocean has its own Bermuda Triangle, the Devil’s Sea, or “Manoumi,” northeast of the Philippines. For decades, ships and planes have vanished there. Some say it’s due to paranormal forces, others blame rough waters and heavy traffic. Either way, it’s as mysterious and perilous as its Atlantic counterpart.

Divya Ramachandran

The Bloop

In 1997, NOAA researchers picked up a mysterious deep-sea sound in the South Pacific, later nicknamed “The Bloop.” Early theories suggested it came from a massive creature, but scientists now think it was icebergs breaking apart. Still, some like to imagine it was Cthulhu stirring in his sleep

National Oceanic and Atmospheric Administration

The Loch Ness Monster

The Loch Ness Monster is one of the world’s most famous mysteries, said to be a dinosaur living in Scotland’s Loch Ness. Reports go back to the 8th century, but it gained fame in 1933 after a photo showed a long-necked creature in the lake.

Some thought it might be a surviving plesiosaur, though scientists say that’s impossible since they went extinct millions of years ago. Despite countless searches, no proof has ever been found—but the legend turned Loch Ness into a booming tourist spot.

Keystone

The Real Atlantis

Atlantis is a legendary kingdom first described by the philosopher Plato. He claimed it was a powerful ancient empire that sank into the ocean after a massive disaster.

Scientists have searched the Mediterranean and the Atlantic for it, discovering many fascinating ruins—but never Atlantis itself.

Many now believe the eruption of the Santorini volcano around 1610 BC, which destroyed the Minoan civilization, could explain the myth. Still, no solid proof has been found.

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The Bermuda Triangle

The Bermuda Triangle is an area in the Sargasso Sea, bordered by Miami, Bermuda, and Puerto Rico, where many ships and planes have mysteriously vanished.

Scientists point to natural causes like methane gas eruptions, rogue waves, and infrasound that can disorient pilots and sailors. Others suggest UFOs or sea monsters, but none of those theories have ever been proven.

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"Milky Sea" Phenomenon

In 2019, the crew and passengers of the superyacht Ganesha became the first to capture the rare “white ocean effect,” in which bioluminescent bacteria glow white rather than blue or green, making the sea look like milk.

Though ancient sailors once described it, only recently have photos and videos confirmed its existence, and scientists still aren’t sure what causes it.

Jess Thomson

Mermaid Sightings Claimed In Israel

Want to make money from strange sightings? Just do what one Israeli city did. After locals in Kiryat Yam claimed to have seen a mermaid, officials offered a reward for a real photo and even erected a statue. The legend became a tourist attraction and a steady source of income.

William Makepeace Thackeray (1811–1863) (not the actual photo)

The Underwater “Pyramid” Near The Azores

In 2013, explorers found a massive 200-foot-tall underwater pyramid near the Azores Islands in the Atlantic Ocean. Since the Azores are linked to the legend of Atlantis, many believed it could be man-made. Scientists, however, say it’s just a natural formation shaped by volcanic activity and ocean currents over time.

Maahid Photos / pexels (not the actual photo)

So, if you ever feel like the world has run out of wonder, just remember this: the biggest livable space on Earth is still mostly uncharted.

There’s something almost poetic about that but more than that, it’s a challenge. Somewhere below the waves, in the cold and crushing dark, there are still stories waiting to be told.