EDITORIAL GUIDE
~5 min read
Unidentified Submerged Objects (USOs) — Underwater UAP in the Official Record
Unidentified Submerged Objects (USOs) — a sub-category of UAP that operates underwater or transitions between air and water — represent some of the strongest physical anomalies in the official record. Conventional aircraft disintegrate on water entry at speed; the fastest known submarine travels approximately 50 mph. Yet multiple sensor-corroborated cases in the official archive document objects moving at hypersonic speed underwater, transitioning between air and water without deceleration, and operating at depths exceeding any known submersible. USO cases appear in NARA RG 615, AARO's unresolved database, and the PURSUE releases.
The Physics of Transmedium Anomaly
The engineering constraint for transmedium objects is severe and well-characterized. When an aerial object enters water at high speed, the drag force is proportional to the density of the medium (water is approximately 800 times denser than air at sea level). At typical aircraft speeds, water entry generates forces that destroy the aircraft structure in milliseconds — the 'water entry problem' is one of the most challenging in aerospace engineering. The fastest known conventionally-powered submarine (the Soviet K-162/K-222) achieved approximately 51 mph submerged; nuclear submarines typically operate at 25–30 mph tactical speed.
The documented UAP transmedium cases show objects performing the water-entry transition without deceleration detectable by radar or sonar sensors. The USS Princeton's SPY-1 Aegis radar tracked the Nimitz Tic Tac descending from 80,000 feet to near sea level and ascending repeatedly — behavior consistent with transmedium operation. Commander Fravor observed the Tic Tac hovering over a circular ocean-surface disturbance, consistent with an object at or near the surface that had recently transitioned from underwater. None of these observations are consistent with known aerodynamic or hydrodynamic engineering.
SOSUS and Sonar Tracking Records
The Sound Surveillance System (SOSUS) — the Cold War-era hydrophone network deployed across the Atlantic and Pacific ocean floors to track Soviet submarines — has produced multiple UAP-related detections in declassified records. SOSUS operates by detecting acoustic signatures propagated through the SOFAR (Sound Fixing and Ranging) channel, which allows detection of objects thousands of miles away.
The Shag Harbour, Nova Scotia incident (October 4, 1967) is the most extensively documented SOSUS/USO case in the North American record. After a luminous object was observed entering the water by multiple civilian and RCMP witnesses, U.S. SOSUS reportedly tracked an unidentified underwater contact moving approximately 25 miles underwater before it surfaced and departed. Canadian and U.S. naval vessels were dispatched but located nothing. The SOSUS tracking records are cited in RCMP and Canadian defence documents; the underlying U.S. SOSUS records have not been publicly released in full. The Shag Harbour case appears in AARO's database as officially unresolved.
USS Russell and Recent Transmedium Cases
The USS Russell (DDG-59) incident (2021) is the most recent high-profile USO case in the public record. Multiple crew members on the guided-missile destroyer observed pyramid-shaped or triangular objects around the ship at night. FLIR footage captured from the ship shows objects in flight. One object appeared to descend into the ocean in the FLIR footage — though the specific moment of entry is contested in public analysis.
The USS Russell footage was first publicly reported in 2021 and subsequently appeared in the PURSUE archive releases. AARO designated the Russell case as unresolved. The pyramid-shape designation and multiple-crew-member corroboration makes it one of the few post-2020 transmedium cases with both video documentation and crew witness accounts.
The PURSUE R02 batch (May 2026) includes a reference to a 'USS Pacific Transmedium 2023' case — an event in the Pacific carrier operating area where an object entered the ocean and was subsequently tracked by sonar at 900 meters depth before re-emerging. The full sensor record for this case remains classified.
USO Classification in the Official Archive
AARO's behavioral taxonomy includes 'transmedium' as one of the defined observable behaviors, based directly on Luis Elizondo's Five Observables framework from AATIP. Cases designated as transmedium in AARO's database represent a subset of total UAP cases — fewer than 10% of AARO's unresolved cases carry the transmedium designation, but those cases consistently rank among the highest-evidential.
The NARA RG 615 archive includes records from the Navy's specialized maritime surveillance systems that are not available through standard FOIA requests to DoD. The RG 615 mandate requires agencies to transfer UAP-relevant records including those from specialized ocean surveillance platforms. How much USO-related material will emerge from these transfers — particularly SOSUS historical records — is one of the most significant unknowns in the coming archive releases.