Underwater USOs: The Transmedium Problem
The U.S. Navy has documented objects entering and exiting the ocean at speeds no known submarine can achieve. The government now uses the term ’transmedium’ to describe objects that move seamlessly between air and water.
What Are USOs?
Unidentified Submersible Objects (USOs) — sometimes called Unidentified Submerged Objects — are anomalous objects observed entering, exiting, or operating beneath bodies of water at speeds and depths that no known submarine or underwater vehicle can achieve.
The term has been used informally for decades, but it entered official vocabulary when the U.S. government began using the term “transmedium” to describe objects that move between air and water (and potentially space) without apparent loss of performance.[1]
The 2023 National Defense Authorization Act (NDAA) defined UAP as:
“Unidentified anomalous phenomena… including airborne, transmedium, or submerged objects or devices that are not combatant combatant command or combatant command identified.”
The inclusion of “transmedium” and “submerged” in federal law was deliberate. These are not hypothetical categories — they reflect what military personnel have reported.
Documented Incidents
The USS Nimitz Encounters (2004)
The famous Tic Tac encounter off San Diego included an often-overlooked detail: before Commander David Fravor’s visual contact with the object, the USS Princeton’s radar operators had been tracking anomalous contacts for approximately two weeks.[2]
Senior Chief Kevin Day, the Princeton’s radar operator, described the objects as descending from approximately 80,000 feet to sea level in less than a second — and in some cases continuing into the water. Multiple radar operators observed objects operating above and below the ocean surface.
During Fravor’s encounter, the Tic Tac object was initially observed hovering over a disturbance in the water — described as a cross-shaped churning pattern just below the surface, as though something large was submerged beneath.
The Puerto Rico USO (2013)
Infrared footage captured by a U.S. Customs and Border Protection aircraft near Rafael Hernández Airport, Aguadilla, Puerto Rico, shows an object travelling at approximately 100 mph, entering the ocean without any splash or deceleration, briefly moving underwater, splitting into two objects, and then re-emerging.[3]
The footage was captured on a DHC-8 aircraft’s thermal imaging system and was analysed by the Scientific Coalition for UAP Studies (SCU), which concluded the object’s behaviour was inconsistent with any known drone, bird, or conventional aircraft.
Key observations from the analysis:
- The object entered the water at speed without visible deceleration or splash
- It appeared to travel underwater for a brief period before re-emerging
- It appeared to split into two objects while submerged
- Water temperature differential was visible on thermal imaging where the object entered and exited
The USS Omaha Incident (2019)
In July 2019, the USS Omaha (a Littoral Combat Ship) documented a spherical object on radar that descended toward the ocean surface and appeared to enter the water. The ship launched a submarine to search the area — no wreckage or debris was found, suggesting the object did not crash but rather transitioned into the water intact.[4]
Filmmaker Jeremy Corbell obtained and released video of the Omaha incident, confirmed as authentic by the Pentagon.
Broader Navy Reports
Multiple Navy personnel have described, in congressional testimony and media interviews, encounters with objects that:
- Enter the water at high speed without visible deceleration or splash effects
- Exit the water at high speed without the expected surfacing dynamics
- Operate at depths and speeds inconsistent with any known submarine (the fastest known submarine reaches approximately 35–40 knots; reported USOs have been estimated at hundreds of knots)
- Show no propulsion signatures — no cavitation, no wake, no exhaust
The Physics Problem
The transmedium aspect of USOs is particularly challenging for conventional explanation because of the physics of air-water transition.
Why Transmedium Is Hard
Moving from air to water (or vice versa) at high speed involves enormous physical forces:
- Water is approximately 800 times denser than air — an object entering water at speed experiences catastrophic deceleration forces
- The air-water interface at high velocity acts effectively as a solid surface (this is why belly-flops hurt and why ballistic missiles designed for water entry require specialised nose cones)
- Hydrodynamics and aerodynamics require fundamentally different design principles — a shape optimised for one medium is typically suboptimal for the other
- Propulsion systems that work in air (jet engines, propellers) don’t work underwater, and vice versa
An object that transitions between media at speed without deceleration, splash, or visible propulsion change implies either:
- A technology that can reduce drag to near zero in both media (possibly through some form of field effect or boundary layer manipulation)
- A technology that can operate with equal efficiency in fluids of radically different density
- Some form of medium displacement that prevents direct contact between the object and the surrounding fluid
None of these capabilities exist in known human technology.
Supercavitation
The closest conventional analogy is supercavitation — a technique used in some Russian torpedo designs (the VA-111 Shkval) that creates a gas bubble around a submerged object to reduce drag. Supercavitating torpedoes can reach approximately 200 knots underwater.
However, supercavitation:
- Requires a conventional propulsion system
- Creates a visible and detectable cavitation envelope
- Does not enable air-to-water transition at speed
- Does not explain the other observed characteristics (no propulsion signature, no wake)
The Government Response
The inclusion of “transmedium” and “submerged” in the NDAA’s UAP definition is significant because:
- It acknowledges that military personnel have reported objects operating in and between these media
- It directs the All-domain Anomaly Resolution Office (AARO) to investigate such reports
- It treats the underwater dimension of the UAP problem as equally serious as the airborne dimension
In congressional testimony, multiple witnesses have referenced underwater encounters. Rear Admiral Tim Gallaudet, a former head of the Naval Meteorology and Oceanography Command, has stated publicly that USOs represent a significant area of concern and that the ocean dimension of the phenomenon is underinvestigated.[5]
What We Know and Don’t Know
| Documented | Undocumented |
|---|---|
| Military radar and infrared recordings of objects entering/exiting water | Physical recovery of a transmedium object |
| Congressional testimony from military personnel | Scientific analysis of propulsion mechanism |
| Pentagon-confirmed footage (USS Omaha) | Peer-reviewed physics explanation |
| Legislative language specifically addressing transmedium objects | Controlled observation under scientific conditions |
| Multiple independent incidents across different platforms and years | Any conventional technology capable of these behaviours |
The USO/transmedium question is in the same epistemic state as the broader UAP topic: military sensor data and testimony exist, but no physical evidence has been made available for independent analysis.
Research Verdict
| Assessment | Documented by military sensors — physics unexplained |
| Confidence | Moderate |
| Summary | Multiple U.S. military platforms have recorded objects exhibiting transmedium behaviour. Congress has legislated the category into existence. The physics of seamless air-water transition at speed are not achievable with any known technology. The evidence is sensor-based and testimonial; no physical samples or controlled observations exist. |
Sources
- Congress.gov — National Defense Authorization Act 2023, UAP provisions (transmedium definition).
- HISTORY — “The Nimitz Encounters” — USS Princeton radar tracking.
- The Black Vault — Aguadilla, Puerto Rico USO incident, 2013.
- Mystery Wire — USS Omaha spherical UAP incident, 2019.
- Gallaudet, T. Written testimony to House Committee on Oversight and Accountability, November 2024.