USO stands for unidentified submerged object. As the name suggests, it is an unidentified object submerged in water. Note that sometimes the term unidentified submarine object is used.

Unidentified in this context does not mean extraterrestrial or paranormal. It is likely that many USOs may be as yet unidentified sea creatures.

Still, there is a considerable overlap with UFOs in that many UFOs are seen rising from the water or disappearing into it.

A USO incident that got a lot of attention in recent years, was Navy Commander David Fravor's encounter.

Two other famous incidents were in Shag Harbor, Nova Scotia, Canada, and in Sognefjord, Norway.

See also: and