USOs: The underwater mysteries that have baffled for centuries
From Columbus’s mystery light to the Tic Tac incident, here’s the history of USOs, the underwater UFOs Bradley Walsh investigates in Out of This World.
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Is the truth really ‘out there’? Quite possibly, but where exactly? You might be tempted to look to the skies. However, this could be the wrong place to look for those aliens. They’re probably not turning up in flying saucers, or even flying at all…
Rather, those little green men could be lurking deep under the sea. An odd choice of place for them to hang out? Not really, if you think about it. Though the ocean covers more than 70% of Earth’s surface, we humans have mapped less than a third of the global seafloor as of 2026.
This all leaves plenty of potential hiding places underwater for aliens eager to keep a sneaky eye on us. In the new Sky HISTORY series Out of This World, TV favourite Bradley Walsh investigates the phenomenon of USOs (unidentified submerged objects). What do the most famous USO cases tell us about what could really lie beneath the waves?
What is a USO?
As you likely already know, the acronym UFO is commonly used to refer to an unexplained aerial phenomenon. The similar acronym USO stands for ‘unidentified submerged objects’. A USO is an unexplained phenomenon detected either in the sea or emerging from it. This makes a USO essentially an aquatic version of a UFO.
Just like a UFO, a USO does not necessarily have to be extraterrestrial in origin. Indeed, many initially mysterious USOs may turn out to be familiar entities like fish, sharks and whales. It’s also possible that relatively uncharted stretches of the ocean are harbouring earthly sea creatures currently unknown to science.
This has not stopped ufologists from speculating that extraterrestrial visitors may also be in our waters. There’s even the frightening prospect of aliens setting up permanent underwater bases. In 2014, one roughly three-mile-wide formation on the seabed floor near California’s Malibu coast attracted suspicion due to its artificial, shelf-like appearance. Nonetheless, geological experts have insisted that this allegedly alien-built ‘anomaly’ could still easily be nature’s doing.
The surprisingly long history of USOs
If you’ve seen a USO, you can report it on the mobile app Enigma, which has logged over 11,000 such sightings off the US coast since 2022. Have USO incidences become more common in recent years? It’s easy to get that impression from the news, but it might just be that we’re becoming more adept at picking up on the phenomena.
Evidently, USO stories have been breaking cover for centuries, long before humans were strapping on scuba-diving gear to explore shipwrecks. While at sea in 1492, Christopher Columbus wrote in his journal about witnessing a peculiar light hovering above the surface of the sea. The explorer likened the sight to ‘a small wax candle rising and falling’.
The Japanese may even have had a close encounter with a seaborne alien in 1803. That’s when a spacecraft-like vessel bearing a feminine mermaid-like creature allegedly washed up on Japan’s eastern coast.
In 1825, Andrew Bloxam was on a sea voyage when he reportedly saw a large, luminous orb appearing to rise from the water. According to the English naturalist, the USO was so fiercely bright it resembled a ‘red-hot’ cannon shot.
The best-known USO cases
Since 2004, the US military has periodically spotted bizarre, lozenge-shaped USOs darting above (and into) seas just off the US mainland. The most famous such sighting is the 2004 ‘Tic Tac’ incident captured on infrared video and radar, which did not attract mainstream attention until 2017.
There’s also the curious case of the ‘Baltic Sea anomaly’, a spaceship-like structure found on the Baltic seabed in 2011. Though sceptics have dismissed it as simply an odd-looking rock, its unusually precise shape has drawn humorous comparisons to the Millennium Falcon from Star Wars.
In one Out of This World episode, Bradley Walsh learns about the ‘ghost rockets’ seen in the skies of Scandinavian countries in 1946. These USOs resembled cigars and were seen falling into lakes. However, no debris from these USOs was ever definitively found at the bottom of these lakes, despite extensive searches that did uncover apparent impact pits.
Crucially, the ‘ghost rockets’ were seen shortly after the end of World War II. The Soviet Union, one of the victorious Allied powers, had only recently recovered German-made weapons. This sparked speculation that at least some of the ‘ghost rockets’ were actually V-1-type missiles being tested by the Soviets.
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