The Baltic Sea Anomaly: What's Sitting on the Ocean Floor?

In the summer of 2011, a Swedish treasure hunting team was scanning the floor of the northern Baltic Sea with sonar, looking for old shipwrecks. What they found instead was something they couldn't explain: a roughly circular object, about 60 meters (200 feet) across, sitting 91 meters (300 feet) below the surface. The sonar image looked, to many observers, uncannily like the Millennium Falcon from Star Wars. Even stranger, the object appeared to sit at the end of a 300-meter track on the seabed, as if something had skidded to a stop on the ocean floor.

The discovery set off a wave of speculation that hasn't entirely died down. Was it a crashed UFO? A secret military installation? An ancient artifact from a lost civilization? Or was it just a funny-shaped rock? More than a decade later, the Baltic Sea anomaly remains one of the internet's favorite ocean mysteries, and the full truth is murkier than the waters it sits in.

What You'll Learn

• •Who Found the Baltic Sea Anomaly?
• •What Did the Sonar Image Actually Show?
• •Did Electronics Really Stop Working Near It?
• •The Glacial Deposit Theory
• •Could It Be a Crashed UFO?
• •Other Theories: Volcanoes, WWII Structures, and Pillow Basalt
• •What Makes This Case Controversial
• •Has Anyone Actually Gone Down to Look?
• •Frequently Asked Questions

Who Found the Baltic Sea Anomaly?

The Baltic Sea anomaly was discovered by Peter Lindberg and Dennis Åsberg, co-founders of the Ocean X Team, a Swedish deep-sea exploration company that specializes in finding sunken shipwrecks and lost cargo. They'd been working the Baltic for years, using side-scan sonar to map the seafloor and locate historically significant wrecks.

During an expedition in June 2011, while scanning the bottom of the Gulf of Bothnia (the body of water between Sweden and Finland), they picked up something unusual on their sonar readout. The image showed what looked like a large, disc-shaped formation resting on the seafloor at a depth of about 91 meters. Below the object, the seabed appeared to show a long, flattened track stretching roughly 300 meters, as though the object had slid into its current position.

Lindberg and Åsberg didn't immediately rush to call it a UFO. In early interviews, they were cautious, noting that sonar images can be misleading and that they needed to return with better equipment. But the image was striking enough that when it hit the internet, speculation took on a life of its own.

The Ocean X Team describes itself as "a world-leading deep-sea exploration company dedicated to uncovering lost treasures, historical shipwrecks, and underwater anomalies." They've found genuine shipwrecks before, including a Russian submarine from World War I. So they weren't amateurs playing around with a fish finder. That said, their sonar equipment would later come under serious scrutiny from oceanographers.

What Did the Sonar Image Actually Show?

Here's where things get tricky. The original sonar image, which is the only one most people have ever seen, shows a roughly circular shape about 60 meters in diameter. It appears to have angular edges, ridges, and features that look almost architectural. When tabloid newspapers got hold of it, someone helpfully drew outlines on the image that made it look even more like a spacecraft, and the comparison to the Millennium Falcon stuck.

But sonar images aren't photographs. They're acoustic reconstructions of the seafloor based on how sound waves bounce back to a receiver. The quality depends heavily on the equipment, how it's calibrated, the speed of the vessel, water conditions, and a dozen other variables. A rocky outcrop, a cluster of boulders, or even a dense school of fish can produce images that look artificially structured when they're nothing of the sort.

Hanumant Singh, a researcher at the Woods Hole Oceanographic Institution, reviewed the sonar data and wasn't impressed. He stated that the image "cannot be trusted" because the sonar instrument used was cheap, improperly wired, and poorly calibrated. According to Singh, the resulting distortions rendered the image "virtually useless for identifying an undersea formation."

That's a pretty damning assessment from one of the world's leading experts in underwater imaging technology. But it didn't slow down the speculation.

Did Electronics Really Stop Working Near It?

One of the most dramatic claims made by the Ocean X Team was that when they returned to the site, their electronic equipment malfunctioned directly above the object. Their satellite phone, cameras, and other devices allegedly stopped working whenever they were within about 200 meters of the anomaly, then started functioning normally once they moved away.

If true, this would be genuinely strange. Electromagnetic interference at that level from a seafloor object would suggest something very unusual about its composition or origin. It's the kind of detail that fuels UFO speculation because it sounds like something straight out of a science fiction movie.

However, there's no independent verification of these claims. No other research vessel has reported similar interference in the area. Electronic equipment on ships can malfunction for all sorts of conventional reasons: atmospheric conditions, equipment age, power supply issues, or simply being in a remote area with poor satellite coverage. The Gulf of Bothnia isn't exactly a telecommunications hotspot.

Skeptics have pointed out that the electronic interference story conveniently makes the anomaly seem more mysterious, which wouldn't hurt if you were, say, trying to fund a return expedition or attract a television production deal. That might sound cynical, but it's a fair point given what came later.

The Glacial Deposit Theory

The most widely accepted scientific explanation is that the Baltic Sea anomaly is a glacial deposit, essentially a big pile of rocks left behind by ice age glaciers.

This isn't as boring as it sounds. During the last ice age, massive ice sheets covered all of Scandinavia and most of northern Europe. As these glaciers advanced and retreated over thousands of years, they carved out the Baltic Sea basin and deposited enormous quantities of rock, sediment, and debris across the seafloor. These deposits come in all shapes and sizes, and some of them look remarkably regular or geometric, even though they're entirely natural.

Volker Brüchert, an associate professor of geology at Stockholm University, analyzed rock samples that the Ocean X Team brought back from the site. His findings? Most of the samples were granites, gneisses, and sandstones, exactly the kind of rocks you'd expect to find in a glacial basin. There was one piece of basaltic (volcanic) rock, which was a bit unusual for the area, but Brüchert explained that glaciers routinely transport rocks hundreds of miles from their point of origin.

"Because the whole northern Baltic region is so heavily influenced by glacial thawing processes, both the feature and the rock samples are likely to have formed in connection with glacial and postglacial processes," Brüchert told Live Science. "Possibly these rocks were transported there by glaciers."

Swedish geologists Fredrik Klingberg and Martin Jakobsson backed this up, noting that the chemical composition of the samples resembled common sea-bed nodules. The minerals found, including limonite and goethite, can form naturally without any help from extraterrestrials.

Finnish planetary geomorphologist Jarmo Korteniemi added another piece to the puzzle. He explained that the "runway" formation beneath the anomaly, the long track that made it look like something had crash-landed, is actually part of a larger group of similar mounds oriented in the same direction on the Bothnian Sea floor. These formations are called drumlins, elongated hills shaped by glacial movement. They're found all over formerly glaciated regions, from Scotland to Minnesota.

Could It Be a Crashed UFO?

Let's address the elephant in the room. Or rather, the Millennium Falcon on the sea floor.

The UFO theory gained traction partly because of the object's shape (round, disc-like, seemingly artificial) and partly because of the alleged electronic interference. Some proponents suggested it could be a spacecraft that crashed into the Baltic Sea thousands of years ago, sliding across the seabed and leaving the 300-meter track behind it.

It's a fun idea. It's also one that doesn't hold up well under examination.

First, the shape. We're working from a single, low-quality sonar image that experts have called "virtually useless." Seeing a disc shape in a blurry sonar readout is a bit like seeing a face in a cloud. Our brains are wired to find patterns and familiar shapes, even where none exist. This tendency, called pareidolia, is behind everything from the Face on Mars to the Virgin Mary on a piece of toast.

Second, the materials. Every sample analyzed from the site has been identified as ordinary rock. No unusual metals, no exotic alloys, no materials that couldn't be explained by natural geological processes.

Third, the track. If something had crash-landed and skidded 300 meters across the seafloor, you'd expect significant disruption to the sediment and possibly fragments scattered along the path. What we actually see is a drumlin formation that's consistent with glacial geology and matches other similar features in the area.

Fourth, the electronic interference. It's an unverified claim from the same team that stood to profit from keeping the mystery alive. Without independent confirmation, it's just a story.

That said, it's worth noting that some genuinely puzzling objects have been found on the seafloor over the years. The ocean is still largely unexplored, and writing off every anomaly without thorough investigation would be just as unscientific as jumping to conclusions about aliens.

Other Theories: Volcanoes, WWII Structures, and Pillow Basalt

Beyond glacial deposits and UFOs, several other theories have been floated:

Volcanic Formation: The basaltic rock sample led some to suggest the object might be related to volcanic activity. However, Jarmo Korteniemi ruled this out pretty decisively. The Fennoscandian Shield, the geological bedrock underlying the Baltic, is a thick, stable craton that hasn't seen active volcanism since the Proterozoic era, roughly 500 million years ago. There's no volcanic plumbing anywhere near the anomaly.

WWII or Cold War Military Installation: The Baltic Sea saw heavy naval activity during both World War II and the Cold War. Some suggested the object could be a sunken gun turret, a concrete submarine base, or some other military structure. It's not impossible in principle, as the Baltic is littered with wartime relics, but no military records support the existence of any installation at that location, and the rock samples don't include any concrete or manufactured materials.

Pillow Basalt: This is a type of rock formation that occurs when lava erupts underwater, forming rounded, pillow-shaped lumps. Some geologists initially suggested this as a possibility, but the absence of active volcanism in the region makes it unlikely that any recent pillow basalt would form there. Ancient pillow basalt transported by glaciers is technically possible but hasn't been confirmed.

Natural Rock Outcrop: Perhaps the simplest explanation. Charles Paull of the Monterey Bay Aquarium Research Institute suggested the sonar image by one account shows a rock outcrop, sediment from a fishing trawler, or even a large school of fish. He characterized the whole story as "curious and fun, but much ado about nothing."

What Makes This Case Controversial

What makes the Baltic Sea anomaly so frustrating is the gap between what was found and what we can confirm. The sonar images show something genuinely unusual sitting on the ocean floor. The dive team reported equipment failures near the object. But the full picture remains just out of reach.

Jonathan Hill of the Mars Space Flight Facility at Arizona State University raised a pointed question in 2012: "Whenever people make extraordinary claims, it's always a good idea to consider for a moment whether they are personally benefiting from the claim or if it's a truly objective observation."

Hill noted that it would've been simple to break off a piece of the object and have it geologically tested in a lab. If it turned out to be ordinary rock, that result wouldn't exactly help fund future expeditions. He suggested the team had a financial incentive to keep the mystery alive.

And there were financial stakes. The Ocean X Team later explored plans to take wealthy tourists in a submarine to visit the site. Peter Lindberg discussed the possibility of a television production deal in a 2019 interview. The more mysterious the anomaly seemed, the more valuable it became as a brand.

This doesn't necessarily mean the team was being dishonest. They may genuinely believe they found something unusual. But it does mean their claims need to be evaluated with an understanding of the incentives involved, which is just good critical thinking applied to any extraordinary claim.

An MSNBC report went even further, speculating that the graphic outlines drawn on the sonar image by tabloid newspapers, the ones that made it look like a spacecraft, may have done more to shape public perception than the actual data ever did.

Has Anyone Actually Gone Down to Look?

The Ocean X Team did return to the site in 2012 with better equipment. Divers reportedly went down and collected the rock samples that were later analyzed by Stockholm University. They also took some photographs underwater, though visibility in the Baltic is notoriously poor, and the images they released didn't clarify much.

Göran Ekberg, a marine archaeologist at Stockholm's Maritime Museum, reviewed one of the underwater photos published by Swedish newspaper Expressen and commented: "A natural, geological formation can't be ruled out. I agree the finding looks weird since it's completely circular. But nature has produced stranger things than that."

Martin Jakobsson, a professor of marine geology at Stockholm University, said he'd need to see more material before making an official determination but guessed it was "some sort of sandstone."

What's notable is that no independent scientific expedition has ever visited the site. All of the physical evidence, the sonar images, the rock samples, the underwater photos, everything comes exclusively from the Ocean X Team. For a discovery that generated this much global attention, the lack of independent verification is striking.

Modern deep-sea imaging technology is vastly better than what was available in 2011. High-resolution multibeam sonar and photogrammetry could map the object in extraordinary detail, similar to the stunning 3D scans of the Titanic produced in recent years. If anyone wanted to settle this definitively, the technology exists. The question is whether anyone with the resources thinks it's worth the trip.

What We're Left With

The Baltic Sea anomaly sits in that uncomfortable space between "probably nothing" and "we can't be 100% sure." The weight of scientific evidence points strongly toward a natural glacial formation. The rock samples are ordinary. The sonar image is unreliable. The electromagnetic interference claims are unverified. The team that found it had financial incentives to maintain the mystery.

But it's also true that the object has never been properly surveyed by independent researchers using modern equipment. And the ocean floor, even in relatively shallow seas like the Baltic, still holds plenty of surprises. We've explored more of the Moon's surface than we have of Earth's ocean floors.

If the Bermuda Triangle teaches us anything, it's that the ocean doesn't give up its secrets easily. And if the Tunguska event teaches us anything, it's that sometimes the by one account explanation is the right one, even when it feels anticlimactic.

The Baltic Sea anomaly is probably a rock. But "probably" isn't "definitely," and until someone goes back with the right equipment and an open mind, that small margin of uncertainty will keep this mystery alive.

Frequently Asked Questions

What is the Baltic Sea anomaly?

It's a roughly circular formation about 60 meters across, discovered on the seafloor of the northern Baltic Sea by Swedish treasure hunters in 2011. A blurry sonar image made it look like a disc-shaped object, prompting speculation about UFOs, ancient structures, and other possibilities. Most scientists believe it's a natural glacial deposit.

Is the Baltic Sea anomaly a UFO?

There's no widely accepted evidence supporting the UFO theory. Rock samples from the site are ordinary granites and sandstones consistent with glacial geology. The sonar image that sparked the speculation has been criticized by experts as unreliable and distorted. The electronic interference claims are unverified.

Who discovered the Baltic Sea anomaly?

Peter Lindberg and Dennis Åsberg of the Swedish Ocean X Team found it during a treasure hunting expedition in June 2011. They were scanning the Gulf of Bothnia with side-scan sonar, looking for shipwrecks, when they picked up the unusual formation at a depth of about 91 meters.

Has anyone visited the Baltic Sea anomaly in person?

The Ocean X Team sent divers to the site in 2012 and collected rock samples that were later analyzed by Stockholm University. However, no independent scientific expedition has ever surveyed the site, and all physical evidence comes exclusively from the Ocean X Team.

Why does the Baltic Sea anomaly look like the Millennium Falcon?

Our brains are wired to find familiar patterns in ambiguous images, a phenomenon called pareidolia. The low-resolution sonar image, combined with graphic outlines added by media outlets, made the formation look more spacecraft-like than it probably is. Experts at Woods Hole Oceanographic Institution called the sonar data "virtually useless" for identifying formations.