USO stands for “unidentified submerged object,” while UFO stands for “unidentified flying object.” Both terms are used to describe objects or phenomena that cannot be easily identified, but USOs refer specifically to objects that are seen in the water, while UFOs refer to objects that are seen in the sky. Some people believe that USOs and UFOs are evidence of extraterrestrial life, while others believe that they can be explained by natural phenomena or human error. To date, there is no scientific evidence to support the existence of either USOs or UFOs, and the existence of these phenomena remains a subject of speculation and debate.
Underwater UFOs and Bases
Interesting documentary by UFO HUB about underwater UFOs.