Last Updated on 1 hour ago by TodayWhy Editorial
The short version: While the public debate about UFOs focuses on the sky, the US Navy has been quietly tracking something far stranger for decades — objects that enter and exit the ocean at velocities no submarine can reach, dive to depths no known vehicle can survive, and transition between water and air without slowing down. The US government now has an official name for them: transmedium UAPs. Congress has mandated their investigation. PURSUE’s Tranche 2 already put footage of them on film. Here is the full picture before Tranche 3 arrives.
1. What Is a USO — and Why Does the Definition Matter?
A USO — Unidentified Submerged Object — is the aquatic counterpart to the UAP. The term describes any anomalous object observed entering, exiting, or operating within bodies of water in ways that cannot be explained by known submarine technology, marine biology, or conventional underwater physics.
The US Naval Institute has noted that the Navy technically classifies some underwater contacts as biological — whales and sharks interfering with sonar. But the military encounters discussed in this article are a different category entirely: objects moving at speeds no marine animal or human submarine can sustain, at depths beyond any operational vehicle, executing maneuvers that contradict hydrodynamics.
The definition matters for a specific reason: the most credible USO cases involve objects that are not purely underwater. They transition between air and water, sometimes appearing to operate in both simultaneously. This is why the US government moved away from “USO” toward a more precise technical classification: transmedium objects. Understanding that term is the first step to understanding why these cases are so resistant to explanation.
For the broader context of the US government’s current declassification effort, see our complete guide: Pentagon UFO Files: Complete 2026 UAP Disclosure Guide.
2. Transmedium: The Word That Changed Everything
In 2022, Congress passed the National Defense Authorization Act with a significant provision: it formally directed the newly created All-domain Anomaly Resolution Office (AARO) to investigate transmedium objects — defined as objects operating across multiple physical domains: air, water, space, and ground.
The inclusion of “transmedium” in federal law was not accidental. It reflected years of classified testimony from military personnel describing objects that did not simply fly over water — objects that plunged into the ocean at high speed, continued operating underwater, and then returned to the air. The 2021 ODNI report on UAPs explicitly identified transmedium travel as one of the key observables being tracked by the US military.
What makes this so physically significant? Water is approximately 800 times denser than air. Any object entering water at aircraft speeds would be destroyed by hydrodynamic forces — the same principle that makes belly-flopping from height painful. Yet multiple credible military witnesses describe objects transitioning between ocean and air without slowing, without a splash, and without structural failure. No known propulsion technology or material science accounts for this. NASA’s independent UAP research program has identified transmedium capability as one of the phenomenon’s most scientifically challenging characteristics.
3. The Historical Record: Five Decades of Navy Encounters
USO reports are not a recent phenomenon. The documented record spans more than half a century of US Navy encounters with a consistency that is difficult to attribute to misreporting.
1963 — Puerto Rico submarine chase
During US Navy training exercises off Puerto Rico, a submarine reportedly broke formation to pursue an unidentified underwater contact moving at speeds exceeding 150 knots — nearly four times faster than the fastest submarine of that era. The crew tracked it for four days as it dove to an estimated 27,000 feet depth. It was never identified. The capabilities described remain beyond anything the US Navy fields today.
Late 1980s–2000s — East Coast “fast movers”
Navy sonar operators along the US East Coast logged what they called “fast mover” contacts — underwater signatures moving at velocities far beyond any known submarine, then disappearing. Veteran sonar operator Aaron Amick described them publicly: “There are a lot of odd things in the ocean. So quick you can’t measure the speed. There is no way to measure the speed accurately because there isn’t enough data.” These contacts were logged and largely set aside for lack of explanation.
2014–2015 — US East Coast, “almost daily”
Navy aviators from a fighter squadron flying off the US East Coast reported anomalous objects “almost daily” for an extended period. Lieutenant Ryan Graves, who later testified before Congress in 2023, described objects capable of transitioning from hypersonic speeds to hovering — sometimes observed transitioning into or out of the water. His testimony is corroborated by multiple sensor systems and crew members across different squadrons.
2019 — USS Omaha: first video evidence
Navy personnel aboard the USS Omaha near San Diego recorded infrared video of multiple spherical UAPs swarming the vessel at speeds reported up to 138 knots. One spherical object was observed descending to sea level and entering the water. A Navy search submarine dispatched to the area found nothing. The Pentagon later confirmed the footage as authentic.
4. The Nimitz Incident: Where Air and Water Blur
The 2004 USS Nimitz encounter is the most thoroughly documented UAP event in US military history — multiple witnesses, multiple sensor systems, official Pentagon confirmation. But its underwater dimension is frequently omitted from the standard retelling.
The incident began not in the air but on the USS Princeton’s radar. Objects were appearing above 80,000 feet, then descending to sea level in under a second. Senior Chief Kevin Day, the Princeton’s air intercept controller, tracked objects that appeared to drop from extreme altitude to just above the ocean surface instantaneously — a deceleration profile that would require forces no known material could survive.
Commander David Fravor, the Navy pilot who flew the famous intercept, observed not just the Tic Tac object in the air but what appeared to be a disturbance on the ocean surface directly below it — as if something beneath the water was interacting with the object above. The Tic Tac itself showed no exhaust, no control surfaces, no sonic boom despite apparent supersonic speed, and no heat signature from any known propulsion system.
After Fravor’s intercept, the Tic Tac accelerated away instantaneously — then reappeared at a pre-briefed rendezvous point 60 miles away, a location known only to the air crew at the time. USS Princeton’s SPY-1 radar tracked the entire encounter. The Department of Defense officially confirmed the authenticity of the Nimitz footage in April 2020. The underwater component has never been explained.
5. What PURSUE Tranche 2 Already Showed Us
The PURSUE program’s second release on May 22, 2026 included what may be the first officially declassified footage showing USO behavior in real time. Two clips in particular stand out.
The first — from March 25, 2022 — shows multiple spherical objects in close proximity to a US Navy submarine. The Pentagon’s own notation states the objects’ “varying directions of travel indicate these are not balloons.” The footage reportedly shows some spherical objects moving in and out of the water surface — transmedium behavior by definition. A separate file labeled “UAP USO formation Wiley 2X Zinc” reportedly shows a formation of objects displaying transmedium characteristics and is believed to be held for Tranche 3.
A third Tranche 2 clip shows a spherical UAP pulsing directly over open water — behavior with no conventional aeronautical explanation. Together, these clips constitute the most explicit official visual evidence to date that the transmedium phenomenon is real and ongoing.
For a full breakdown of all Tranche 2 material, see: Pentagon UFO Files Tranche 3: What’s Coming Next After the Shocking Videos?
Video Army UAP 2026
6. Tranche 3: What’s Expected and Why USOs Are Central
As of June 8, 2026, Tranche 3 has not been officially released. The Pentagon committed to releasing files “every few weeks as they are discovered and declassified.” With Tranche 1 on May 8 and Tranche 2 on May 22, Tranche 3 is expected imminently.
Sources familiar with PURSUE indicate USOs will be Tranche 3’s central theme. This fits the program’s apparent narrative structure: Tranche 1 established the breadth of the UAP record; Tranche 2 introduced underwater encounters and raised the evidence quality; Tranche 3 appears positioned to make the transmedium case explicitly.
Specific expected items include the “UAP USO formation Wiley 2X Zinc” file, additional Department of Energy records from nuclear facilities where UAP activity near restricted areas was documented, and possibly more NASA mission audio building on the seven Apollo recordings in Tranche 2.
The US Naval Institute noted in 2022 that “USOs not UFOs have been the greatest threat to the Navy” — a headline that now reads less like editorial exaggeration and more like institutional anticipation of exactly where the PURSUE program was heading.
TodayWhy will update this article the moment Tranche 3 is released. Full PURSUE guide: Pentagon UFO Files: Complete 2026 UAP Disclosure Guide.
7. The Government’s Official Position: AARO and the Transmedium Mandate
The institutional acknowledgment of USO-type phenomena runs deeper than most public coverage reflects. AARO — created by Congress in 2022 — holds an explicit mandate covering air, sea, space, and ground domains simultaneously. It maintains databases of sensor data from Navy vessels, submarines, and maritime patrol aircraft documenting USO activity.
Multiple Congressional hearings since 2022 have addressed the underwater dimension directly: Navy pilots testified about objects entering water during encounters; sensor operators described tracking objects transitioning between air and sea; intelligence officials acknowledged “unexplained underwater contacts in sensitive military operating areas.”
The 2021 ODNI UAP report identified five explanatory categories for UAPs — airborne clutter, natural phenomena, US developmental programs, foreign adversary systems, and a fifth category labeled “other.” The transmedium cases largely fall into that fifth category. No known foreign adversary — including China and Russia — has demonstrated anything close to the capabilities described. The ODNI has been required to submit annual UAP reports to Congress since 2022; the unclassified versions consistently describe transmedium cases as “unresolved.”
8. Rear Admiral Gallaudet: The Highest-Ranking Voice on USOs
Among credentialed voices speaking publicly about USOs, former US Navy Rear Admiral Tim Gallaudet is the most senior. A retired naval oceanographer and former acting NOAA administrator, Gallaudet testified before the House Oversight Committee in November 2024, stating directly that USOs represent “a serious national security risk.”
He has gone further in public interviews, articulating a hypothesis that distinguishes him from most officials willing to speak on the record: that some UAP/USO phenomena may originate not from space but from within Earth’s deep oceans — from a civilization that predates human technological development. “Or why not — maybe they lived here for a long time, before we even evolved,” Gallaudet said, “and sought safety from the Earth’s atmospheric and geologic cataclysms by creating a habitat beneath the seafloor.”
Gallaudet frames this as a hypothesis, not a conclusion. But a retired Rear Admiral making this argument before Congress places USOs in a categorically different institutional space than fringe speculation. His testimony, alongside that of former Defense Intelligence Agency officer David Grusch — who referenced materials recovered from “non-human” craft in his 2023 Congressional testimony — represents the most senior level at which these claims have been officially aired.
9. What Could Explain USOs? The Leading Hypotheses
Natural phenomena and misidentification. Some USO reports almost certainly represent sonar artifacts, biologics, or unusual oceanographic conditions. The Navy’s own classification system acknowledges this. However, multi-sensor, multi-witness events like the 1963 Puerto Rico chase and the 2019 USS Omaha incident are far harder to attribute to sonar ghosts or biological contacts.
Classified US technology. Some researchers argue that the most dramatic USO encounters represent US developmental programs. This is the most institutionally comfortable explanation — but it has a critical problem: the capabilities described remain beyond any publicly known physics, and no such program has been acknowledged in decades of UAP investigations, including under oath before Congress.
Foreign adversary systems. China and Russia have both invested in undersea technology. However, the ODNI has consistently assessed that neither country possesses capabilities matching USO encounter reports. A foreign vehicle performing the Nimitz-era maneuvers would represent a technological leap the US intelligence community would have detected long before deployment.
Non-human origin. The hypothesis that USOs represent technology from an intelligence other than human civilization — whether extraterrestrial or, as Gallaudet suggests, from deep within Earth — is the most extraordinary and therefore requires the most extraordinary evidence. The PURSUE program has not yet provided that evidence. What it has provided is a growing public record of encounters that cannot be explained by the first three hypotheses. That is not confirmation. It is not nothing, either.
The honest scientific position, endorsed by NASA’s UAP research group, is that the current evidence base is insufficient for any definitive conclusion. What is certain is that the Navy has documented genuine anomalies that have resisted explanation for over sixty years.
10. Frequently Asked Questions
What is a USO (Unidentified Submerged Object)?
A USO is an anomalous object observed entering, exiting, or operating in water at speeds or depths no known submarine or underwater vehicle can achieve. The US government’s preferred current term is “transmedium UAP” — objects capable of operating across air, water, and space.
Has the US Navy officially documented USO encounters?
Yes. Congress mandated AARO to investigate transmedium objects in 2022. Multiple naval officers have testified before Congress about objects transitioning between air and sea. PURSUE Tranche 2 included official video of spherical UAPs near a US Navy submarine, with the Pentagon’s own notation ruling out balloons.
What is transmedium travel?
Transmedium travel describes movement across physically different domains — air, water, space — without the structural failure or deceleration that physics demands of any known material. It was formally incorporated into US defense law in the 2023 NDAA, mandating AARO to investigate such objects.
Will Pentagon UFO Tranche 3 show USO footage?
Sources indicate Tranche 3 will focus heavily on USO encounters. The “UAP USO formation Wiley 2X Zinc” file is expected in the next release. Tranche 2 already previewed the theme with submarine footage and a spherical-object-over-water clip.
What are the most credible historical USO cases?
The strongest cases: 1963 Puerto Rico submarine chase (150+ knots, four-day track to 27,000 ft); 2004 USS Nimitz (objects from 80,000 ft to sea level in under a second, with reported underwater activity); 2019 USS Omaha (138-knot spherical UAPs, one entering the water); and the 2022 submarine video in PURSUE Tranche 2.
Continue reading — Why UFO series:
- Pentagon UFO Files Tranche 3: What’s Coming Next? — Full PURSUE disclosure breakdown and what to expect when Tranche 3 drops.
- Pentagon UFO Files: Complete 2026 UAP Disclosure Guide — Every tranche, NSA records, and all 51 Tranche 2 videos explained.
- NSA Top Secret UMBRA UAP Records: What the 2026 FOIA Release Reveals — The parallel NSA disclosure running alongside PURSUE.