Underwater Drone Threats to Port Infrastructure: An Emerging Risk

Underwater drone threats to port infrastructure represent an emerging risk category that most port security frameworks are not designed to address. Unmanned underwater vehicles (UUVs) — also known as autonomous underwater vehicles (AUVs) when operating without a tether — have matured from expensive military and scientific research tools into increasingly affordable platforms available to state actors, non-state groups, and even commercial entities. Their potential to survey, sabotage, or destroy underwater port infrastructure including pipelines, cables, jetty pilings, and vessel hulls makes them a threat that terminal operators can no longer afford to ignore.

While no publicly confirmed UUV attack on port infrastructure has occurred as of early 2026, the technology trajectory and demonstrated use in adjacent domains — underwater cable damage, naval mine deployment, and military reconnaissance — indicate that it is a matter of when, not whether, this threat materializes.

What Are Underwater Drones?

Underwater drones fall into several categories:

Remotely Operated Vehicles (ROVs) are tethered to a surface vessel or shore station via an umbilical cable that provides power, communications, and control. ROVs are widely used in the offshore oil and gas industry for inspection, maintenance, and construction. They range from small observation-class units costing under $50,000 to work-class systems costing millions.

Autonomous Underwater Vehicles (AUVs) operate without a tether, navigating autonomously using pre-programmed waypoints, inertial navigation, and onboard sensors. AUVs are used for hydrographic survey, mine countermeasures, environmental monitoring, and military reconnaissance. Costs range from $100,000 for small commercial units to millions for military-grade systems.

Gliders are a specialized AUV type that use buoyancy changes rather than propellers for propulsion, enabling very long endurance (months) at the cost of speed. They are primarily used for oceanographic research but have intelligence applications.

Swimmer Delivery Vehicles (SDVs) are manned or unmanned submersibles designed to transport divers or payloads to underwater targets. Military special operations forces use SDVs for harbor penetration and underwater sabotage.

Why Are Underwater Drones a Threat to Ports?

Subsurface Infrastructure Vulnerability

Modern ports depend on underwater infrastructure that is largely unmonitored:

• Subsea pipelines carrying oil, gas, water, and effluent to and from the terminal.
• Submarine power and telecommunications cables connecting island terminals, offshore facilities, and transoceanic networks.
• Jetty and wharf pilings — the structural foundations supporting berths and loading equipment.
• Intake and outfall structures for cooling water, ballast water, and LNG regasification systems.
• Vessel hulls of ships at berth, which can be used to attach explosive devices (limpet mines) or smuggling containers.

A UUV can survey these assets to map vulnerabilities, deliver explosive charges to critical points, or physically damage structures through impact or tool-based attack.

Detection Is Extremely Difficult

Underwater detection is fundamentally harder than surface or aerial detection. Sonar — the primary underwater sensing technology — has significant limitations in the shallow, cluttered, noisy environments typical of ports:

• Acoustic clutter from vessel traffic, harbor works, marine life, and reflections off hard surfaces creates false contacts and obscures genuine threats.
• Limited range in shallow water, where sound propagation is heavily affected by temperature gradients, salinity changes, and bottom reflections.
• Small target signatures. A UUV the size of a torpedo or smaller produces an acoustic signature that is difficult to distinguish from environmental noise at useful detection ranges.

Low Barrier to Entry

Commercial AUV technology is accessible and affordable. A capable survey-class AUV can be purchased for $100,000–300,000. Open-source autopilot software (ArduSub, BlueOS) enables custom builds at even lower costs. While weaponizing a UUV requires additional expertise, the base platform technology is readily available.

Precedent from Adjacent Domains

The Baltic Sea cable and pipeline damage incidents — while attributed to anchor dragging rather than UUVs — demonstrated the vulnerability of subsea infrastructure and the difficulty of attribution. The Nord Stream pipeline sabotage of September 2022, likely involving underwater explosive devices (though the exact method remains disputed), showed that actors are willing and able to attack critical subsea infrastructure.

What Are the Potential Attack Scenarios?

Security assessments for underwater drone threats typically consider:

• Reconnaissance. UUV surveys of port underwater infrastructure to map layout, identify vulnerabilities, and plan subsequent attacks. This may be occurring already without detection.
• Explosive attack. Delivery of explosive charges to critical infrastructure — pipeline connections, jetty pilings, vessel hulls. Even a small charge (5–10 kg) placed at a structural weak point can cause significant damage.
• Limpet mine delivery. Attaching explosive devices to the hull of a vessel at berth, to be detonated remotely or on a timer after the vessel departs.
• Smuggling facilitation. Using UUVs to transport contraband (drugs, weapons) into port areas, bypassing surface and landside security.

How Can Ports Defend Against Underwater Drone Threats?

Effective underwater security requires technologies and practices that most ports have not traditionally deployed:

Sonar surveillance. Fixed and portable sonar systems designed for harbor protection, including diver detection sonar (DDS) that can detect small underwater targets at ranges of several hundred meters. Systems from companies like Sonardyne, DSIT, and Kongsberg are specifically designed for port protection applications.

Underwater barriers. Physical barriers — nets, booms, and bottom-mounted obstacles — that restrict UUV access to critical infrastructure. These are effective but expensive and can interfere with port operations and navigation.

Acoustic deterrents. High-powered acoustic devices that can disorient or disable UUVs (and human divers) at range.

Regular underwater inspections. Periodic diver or ROV inspections of critical underwater infrastructure to detect surveillance devices, attached explosives, or structural damage.

Integration with surface security. Underwater surveillance must be integrated with surface and aerial detection systems to provide a comprehensive security picture that covers all domains.

Key Takeaways

• Underwater drones are an emerging threat to port infrastructure that most security frameworks do not address.
• Critical subsurface infrastructure — pipelines, cables, pilings, vessel hulls — is largely unmonitored at most ports.
• Detection is extremely challenging due to acoustic clutter, limited sonar range in shallow water, and small target signatures.
• The barrier to entry is decreasing as commercial AUV technology becomes more affordable and capable.
• Port operators should assess their underwater vulnerability, invest in harbor protection sonar, conduct regular underwater inspections, and integrate subsurface surveillance with their broader security architecture.