At DSEI 2025 in London, Blue Ocean Research unveiled its SG-1 Fathom underwater glider—an autonomous unmanned underwater vehicle (UUV) designed to deliver persistent undersea surveillance. With a focus on long-endurance missions and modular payload integration, the SG-1 aims to support naval ISR (intelligence, surveillance, reconnaissance), anti-submarine warfare (ASW), and environmental monitoring operations in contested maritime environments.
Design Philosophy and Propulsion Concept
The SG-1 Fathom is based on a buoyancy-driven propulsion system—a hallmark of modern underwater gliders. Unlike conventional UUVs that rely on propellers or thrusters for movement (which consume significant energy), the SG-1 adjusts its buoyancy to ascend or descend through the water column. This vertical motion is converted into forward glide using fixed wings. The result is ultra-low power consumption and mission durations measured in weeks or even months without surfacing.
According to Blue Ocean Research representatives at DSEI 2025, the SG-1 features a composite hull optimized for hydrodynamic efficiency and pressure resistance up to depths of 1000 meters. The glider measures approximately 2.2 meters in length with a wingspan of around 1 meter—dimensions that balance portability with sufficient payload capacity.
Autonomy and Navigation Capabilities
The SG-1’s autonomy stack includes inertial navigation systems (INS), Doppler velocity logs (DVL), GPS synchronization during brief surface intervals, and acoustic positioning support via long baseline (LBL) or ultra-short baseline (USBL) systems. These enable precise navigation even during extended submerged operations where GNSS access is unavailable.
Mission planning is conducted via a secure C2 interface allowing operators to define waypoints, depth profiles, sensor activation schedules, and contingency behaviors in case of anomalies. The onboard AI-based decision engine can dynamically adjust mission parameters based on environmental inputs such as salinity gradients or detected acoustic anomalies.
Modular Payload Bay for Multi-Mission Flexibility
A key differentiator of the SG-1 Fathom is its modular payload architecture. The central payload bay can accommodate a variety of mission-specific sensors including:
- Passive acoustic arrays for submarine detection
- CTD sensors (conductivity-temperature-depth) for oceanographic profiling
- Turbidity and fluorometry sensors for environmental monitoring
- Magnetometers for mine-like object detection
The open architecture supports future integration of synthetic aperture sonar (SAS), side-scan sonar modules or even low-power optical imaging systems depending on mission needs. Data collected can be exfiltrated via Iridium satellite uplink when surfaced or stored onboard until recovery.
Operational Use Cases: From ASW to Climate Monitoring
The SG-1’s endurance—reportedly exceeding 90 days depending on configuration—makes it ideal for persistent maritime domain awareness tasks in both littoral and deep-sea environments. Potential military applications include:
- Pre-positioned ASW picket lines near chokepoints or submarine transit routes
- Covert ISR collection near adversary naval bases without risk to crewed platforms
- Cueing manned ASW assets with real-time acoustic anomaly alerts
Civilian applications are equally viable—such as supporting marine biodiversity studies in remote areas or monitoring illegal fishing activity in EEZs using passive acoustic signatures.
DSEI Debut and Market Positioning Strategy
DSEI 2025 marked the first public appearance of the SG-1 Fathom platform outside classified trials reportedly conducted with NATO partners earlier this year. While Blue Ocean Research has not disclosed specific customers yet, company officials stated interest from several European navies seeking low-cost force multipliers amid growing undersea threats from Russia’s Northern Fleet operations.
The platform competes with established gliders like Teledyne Webb’s Slocum G3 but differentiates itself through deeper dive capability (>1000 m vs ~200 m typical), higher payload volume (~8 liters usable space), and enhanced autonomy software stack tailored for military ISR missions rather than purely scientific research.
Challenges Ahead: Communications & Counter-UUV Threats
A key limitation remains intermittent communications due to the need to surface periodically for data transmission—a vulnerability if adversaries employ satellite tracking or RF triangulation techniques. Additionally, as navies develop counter-UUV tactics including active sonar sweeps or UUV hunter-killer drones like China’s “Sea Hunter” analogues, survivability will depend on stealthy design signatures and evasive programming logic.
Blue Ocean Research indicated ongoing work on encrypted burst-mode communications via low-probability-of-intercept waveforms as well as development of acoustic modems capable of limited submerged data relay between multiple gliders operating cooperatively—potentially forming an autonomous mesh network across large oceanic regions.
Outlook: Autonomous Undersea Networks as Strategic Enablers
The debut of platforms like the SG-1 Fathom reflects a broader shift toward distributed autonomous sensing architectures below the surface—a domain traditionally dominated by expensive crewed submarines or stationary seabed arrays. As great power competition intensifies across Indo-Pacific sea lanes and Arctic passages alike, unmanned gliders offer scalable ISR coverage without risking human lives or escalating tensions through overt presence.
If successfully fielded at scale—with robust comms links back to command centers—the SG-1 could become part of an emerging “underwater internet-of-things” enabling real-time situational awareness across vast maritime spaces previously considered blind zones by traditional navies.
