The video below by Paranormal Crucible shows images from a Navy Submarine crew on board the USS Trepang in 1971 who claimed to have witnessed first hand UFOs / USOs going in and out of the sea. The images are very strange to say the least. The one at 1:53 is very interesting. The Antarctic has been under suspicion for a very long time.There are people who believe aliens have underground bases in many locations worldwide, some reachable under the sea, and some under the ice. Maybe they even have a base in the Middle Earth, as there is said to be a void there which spans thousands of miles..
Maybe all the tunnels lead to the same underground base / hidden world. Who knows for sure. In regards to the Antarctica USOs, there was an abduction case I can recall where the people who were abducted actually spoke to the aliens, and apparently the aliens communicated to the abductees and said "We (the aliens) came from Antarctica. There is a tunnel which travels under the South Pole, and that’s why you seen us coming out from the water." Read the full story about this abduction. Its the last story on that linked page. Or if you want more information on USOs just do a search on Youtube for UFO USO and you will get some interesting results.
Massive USOs have been seen leaving the water and taking off a speed into the sky, then becoming UFOs. One of the first men of the modern era to publicly try and shed light on secret society's, such as the Illuminati to the general public, Milton William (Bill) Cooper claimed that when he was in the military (Navy) he seen a Craft come flying out the water and take off into the sky. Some people thought he was nuts, but the truth was that he was far ahead of everyone else (most people) for his time.
Bill Cooper was an outspoken ex military whistle blower who had serious knowledge on secret society's, secret governments, aliens, cover ups, social engineering, mind control, and how the system is really run. And this was all before the main source, where we get most of our information from today, the Internet, was widespread and available in peoples homes (Late 80s). Today, people can appreciate Bill Cooper more because thanks to the Internet people are now better informed and can educate themselves a lot easier on such matters.
The Internet, and people hungry for the truth has also redeemed Bill Cooper in many ways because of the many excellent videos and channels that are out there on these subjects. Bill Cooper is now, by most seen for what he really was. And that was not a man who was crazy at all, although there are people who think he was delusional. He wasn't perfect by any means. But he was a man with knowledge that had been hidden from the public for a very long time, and a man who wasn't afraid to speak up about it.
And that knowledge had been kept so well hidden, so secret, that any - one - person trying to expose it at that time was looked at as crazy because it was too much for the average person to comprehend. However, it's now clear that he was just a man with a lot to say who was way ahead of anyone else (anyone willing to speak up anyway), that wanted people to know the truth. A lot of people believe that Bill's relentless mission to expose the truth was what ultimately led to his death.
If Bill Cooper seen a USO I tend to believe him because again, he seen a (USO) before the term USO was even created! He was a young man at the time. Later in his life he came to the conclusion that what he seen come out of the sea were man-made crafts engineered by the Governments of the world. Who really knows for sure. Best to keep an open mind. Remember the old saying "the mind is like a parachute, it works best when it is open".