USOs, or “Unidentified Submerged Objects”, an advanced type of UFO that can operate just as efficiently in water as in the atmosphere. These supposed otherworldly vessels have been reported, some believe, as far back as ancient Egypt. Others believe that USOs were reported by Alexander the Great and Christopher Columbus, and might even involve the lost city of Atlantis. Highlights include the 1967 “Shag Harbour Incident”, a government-documented USO crash off the coast of Nova Scotia, Canada, and a trip to the area around Laguna Cartegena in Puerto Rico, a reported hotbed of USO activity. Interviewees include the US Navy’s Bruce Maccabee, UCLA’s Kathryn Morgan, as well as USO and UFO experts Stanton Friedman, Bill Birnes, and Preston Dennett.