A team of Swedish researchers has found what some are calling a UFO under about 300 feet of water between Finland and Sweden. According to a piece in the Vancouver Sun,

“While using sonar to survey the Gulf of Bothnia last month, Ocean Explorer commander Peter Lindberg noticed an unusual 60-foot round object. According to the Ocean Explorer website, Lindberg said he had “never seen anything like it” even though has “spent hundreds of hours watching sonar images of the sea floor.” While the object seems unusual, it’s entirely possible that it could have occurred naturally. Lindberg refused to speculate on the object’s origins, but in doing so he may have generated even more conjecture, making reference to one of the most famous and mysterious sites in the world “Since it might be nothing we cannot afford spending funds just to have a look at it,” he adds. “Even if it might be a ‘new’ Stonehenge standing on the bottom.”

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There are plenty of theories about what the USO (unidentified sunken object) might be. Lindberg offered a “new Stonehenge,” though some suspect it’s a natural formation, such as the rim of a small underground volcano, which certainly create a very round, prominent ring.

Others see clear evidence that the object, whatever it is, is too perfectly round to be anything but man-made. Of course, one of the most popular — and most outlandish — theory is that it’s a crashed extraterrestrial spacecraft.

Yet there’s another theory: the USO is neither an extraterrestrial craft nor a natural feature but instead a rotating gun turret from a World War II era battleship. It’s possible that an explosion on the ship’s deck could have blown it out of the deck ring where it was anchored and it slid into the ocean’s depths, more or less intact. Such an explosion would not necessarily have sunk the ship, so the lack of nearby wreckage may not be a mystery.

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The turret-less ship might have made it back to port, or may have continued to another location where it eventually succumbed and sank. The top-heavy turret would likely have sunk with the cannons face down in the ocean floor, and would not necessarily have been seen in the sonar image. In fact, Lindberg and his crew were originally drawn to the area in search of Swedish merchant ships sunk by the German navy in World War I.

So what is it? Until someone actually goes down to search the object more closely (or recover it) — a potentially time-consuming and expensive proposition — we may never know. It’s a genuine mystery, and, as is often the case, the most mundane explanation may be the most likely.