USO / Transmedium Craft
- First reported
- October 4, 1967 (Shag Harbour, Nova Scotia — the case that established USO as a distinct evidentiary category, backed by an official government search operation)
- Peak decade
- 1960s (Shag Harbour); resurgent 2000s-2020s with Navy transmedium claims around the Nimitz and Aguadilla incidents
Composite silhouette from witness reports
Profile
Not a fixed silhouette but a behavioral category: any craft — disc, sphere, cylinder, or otherwise — reported crossing between air and water (or, in a handful of accounts, air and solid ground) without slowing, breaking apart, or otherwise behaving the way a conventional vehicle must at that boundary. Unidentified Submerged Objects (USOs) proper are witnessed entering or emerging from open water at high speed with minimal splash; transmedium cases more broadly include craft that vanish and reappear across other physical boundaries. The category anchors two of the field's most physically dramatic incidents: Shag Harbour, Nova Scotia, where a lighted object was watched by multiple independent witnesses descending into the Atlantic — treated seriously enough that Canadian naval and coast-guard divers searched the bay for wreckage in the following days — and the 2013 Aguadilla, Puerto Rico infrared video, in which a federal surveillance aircraft's own camera recorded an object diving directly into the ocean and appearing to split into two before doing so.
Skeptical reading
Shag Harbour's most likely mundane candidate is a flare, meteor, or piece of falling debris striking the water — the multi-day naval search found no wreckage of any kind, and Canadian defense documents released decades later categorize the case as an unresolved 'UFO' rather than confirming a submerged craft. The Pentagon's own 2023-24 review of the Aguadilla video, reported by AARO, concluded the object most likely never entered the water at all — that its apparent 'splash' and dive were an optical parallax artifact of the aircraft's own camera pod passing in front of a distant, ordinary flying object, a conclusion that directly undercuts the case's signature transmedium claim.