Last month, the United States Navy confirmed formally that two high profile videos allegedly captured from the nose of an F/A-18 Super Hornet attempting an intercept on an Unidentified Aerial Phenomena were real and notably, weren’t meant for release to the public. The Navy did not suggest that the strange craft shown in the videos was alien in origin, but rather did acknowledge that they truly didn’t know what they were seeing that night in January of 2015.

“I truly thought the official word on these videos would be ‘drones’ or something similar; but explainable,” John Greenewald, Jr, who runs the popular website The Black Vault, told SOFREP at the time. Greenewald was the man that got the Navy to discuss the videos, leading to a landslide of headlines throughout the media in the weeks that followed.

“We have official documents that have surfaced through FOIA that state just that. However, for the Navy to contradict that, and say that this ‘phenomena’ represents something ‘unidentified’ – that’s pretty amazing to me and proves yet again why we can’t lock ourselves into any one way of thinking or assume anything.”

Reports of unusual lights in the sky date all the way back to the beginning of recorded history, but there’s another unusual phenomena that often seems to coincide with these strange sightings that gets far less attention in the press: USOs, or Unidentified Submerged Objects. Like UFOs (Unidentified Flying Objects), USO is a sort of catch-all term used to describe anything seen operating beneath the surface of a body of water that defies explanation. Legends of USOs have permeated the maritime community for centuries, and remain a common facet of discussion among UFO researchers to this day. In fact, many UFO witness statements, including those provided by military aviators, have suggested that the unusual crafts they’ve spotted flying in the sky seem to operate just as readily in the far denser medium of water — suggesting that these unusual objects can function beneath the surface of the ocean just as well as they can in the air.

Even Christopher Columbus reportedly had a USO sighting during his 1492 voyage to the Americas. According to Columbus’ log, he spotted “a small wax candle that rose and lifted up, which too few seemed to be an indication of land.” They soon determined that it wasn’t a light source from land, but had instead been out at sea — leading to a centuries-long mystery that stands to this day. A more contemporary sighting near Shag Harbor in the Canadian province of Nova Scotia saw a UFO apparently crashing into the harbor’s waters in front of a number of witnesses in 1967. The Royal Canadian Mounted Police even launched rescue efforts early on, assuming the sightings were of a downed aircraft. Their efforts however, turned up nothing.

If the idea of an unidentified, fast moving craft operating under water seems just a bit too out of this world, you should know that USOs may not even be all that uncommon — the U.S. Navy just doesn’t make a habit of keeping track of them (much like UFOs or UAPs until recently).

Earlier this year, Tylor Rogoway at The War Zone interviewed a number of veteran U.S. Navy submariners, some of whom were SONAR operators with first hand experience spotting these unidentified underwater anomalies. Rogoway was looking for more information pertaining to an unsubstantiated story posted to social media by Tom Delonge, former Blink 182 front man turned UFO researcher and founder of To the Stars Academy — a high profile media think tank that champions disclosure of UFO related materials.

That story can be traced back to UFO researcher Marc D’Antonio, who claimed to be given a courtesy ride on a U.S. Navy fast attack submarine, during which he was present as a sonar operator identified a “fast mover” moving at hundreds of knots under the water in close proximity to the sub. D’Antonio’s story doesn’t quite add up in a number of ways (as one former submariner points out in Rogoway’s piece, “we don’t give ‘rides’ as favors”) but his account of a fast moving, unidentified object spotted by Navy personnel and then disregarded seems to ring true with those that have spent time operating America’s undersea vessels.

I don’t know what they are… We usually logged it as seismic or biologic. We were instructed that nothing is ever ‘unknown.'” Explained a former submariner turned professional gamer that now goes by the name “Jive Turkey.”

“That’s the thing, it’s so quick you can’t measure the speed. In the examples I am thinking of, it is a detection that lasts a few seconds on the towed array. There is no way to measure the speed accurately because there isn’t enough data… I agree it’s odd. There are a lot of odd things in the ocean. Mainly, submariners!”

US Navy reveals the truth about two infamous UFO videos

Read Next: US Navy reveals the truth about two infamous UFO videos

Jive Turkey’s funny name notwithstanding, he’s not the only former submariner to acknowledge unusual readings from America’s nuclear submarines that suggested they weren’t alone in the water. Unsurprisingly, however, these anomalies tend to go ignored unless they represent a threat to the vessel or an obstacle between the crew and accomplishing their mission. The ocean is vast, full of man made ships and living creatures, and things like sound travel differently through water than they do through air. As a result, living and working beneath the waves comes with a certain acceptance of the eerie as a new “normal.” In other words, strange is just a part of business when you’re operating a fast attack sub.

In the minds of some, these sightings are related to other unexplained ocean phenomena, like the infamous “Bloop” — which was a massive underwater sound recorded in 1997. The sound was so loud that it was recorded simultaneously on underwater microphones located more than 3,000 miles apart. In the years since, the Bloop has been explained away as an underwater earthquake or tectonic shift, but some remain unconvinced.

According to Navy submariners, standard operating procedure doesn’t allow for the exploration of strange readings that pop up on sonar or other systems, and there is no procedure established for the further investigation of these sightings. That means that unusual objects beneath the surface of the ocean largely go unreported altogether, provided whatever is spotted doesn’t appear as though it will interfere with the mission.

Without reporting guidelines and government disclosure, we may never know if USO sightings are highly rare or entirely commonplace, but submariner accounts confirm that weird stuff is normal in the dark depths of Earth’s oceans. Just like with sightings in the sky, weird doesn’t have to mean alien — it just means unexplained… for now.