Harbor Defense: Integrated Underwater Domain Awareness for Critical Infrastructure (Gemini)
Securing high-value port assets against asymmetric underwater threats by integrating acoustic detection with environmental characterization for reliable threat identification.
Key Benefits
Eliminating Vigilance Decrement
Automated classification filters nuisance alarms, preventing the desensitization of security operators who monitor screens for extended shifts.
Detecting Low-Observable Threats
Identifies acoustic signatures of Closed Circuit Rebreathers and dark vessels that evade conventional surface radar and visual lookouts.
Enabling Dynamic Force Posture
Provides the Captain of the Port with verified threat data to justify escalating MARSEC levels or deploying MSST assets to specific sectors.
Confronting the Underwater Black Hole in Harbor Security
While the Captain of the Port (COTP) exercises broad authority under 33 CFR 160.111 to control vessel movement, most Ports, Waterways, and Coastal Security (PWCS) missions operate with a critical blind spot: the underwater domain. Current security architectures rely heavily on surface assets—AIS, radar, and cameras—leaving infrastructure vulnerable to asymmetric threats. Adversaries utilizing Closed Circuit Rebreathers (CCRs) or small Unmanned Underwater Vehicles (UUVs) can bypass surface surveillance entirely. In the context of Underwater Domain Awareness (UDA), most commercial and strategic ports remain a "black hole," lacking the subsurface visibility required to detect diver-placed explosives or hull-attached narcotics parasites.
This vulnerability is exacerbated by the harsh acoustic reality of "brown water" environments. Cold War-era blue water sonar principles fail in tidal harbors where shallow depths, reverberation, and constant commercial traffic create a chaotic acoustic background. Security teams often rely on standalone Diver Detection Sonars (DDS), but environmental variability—such as thermal layering or turbidity plumes—can render these systems ineffective without warning. Furthermore, the high rate of false positives from marine life and debris causes "vigilance decrement," where operators eventually disregard alarms due to the "cry wolf" effect, creating a window of opportunity for sophisticated actors to penetrate the security perimeter.
Layered Defense for Persistent Underwater Domain Awareness
To secure the underwater approaches to critical infrastructure, port authorities require a multi-sensor architecture that fuses acoustic detection with environmental context. By moving away from stovepiped data systems, this solution integrates passive listening with environmental characterization to distinguish actual threats from background clutter, enabling a "tip and cue" capability that validates targets before alerting human operators.
Data Collection & Monitoring
Fixed sensor nodes attached to pilings and channel markers create a persistent listening grid across the harbor. Hydrophone arrays capture acoustic signatures, while collocated environmental sensors monitor water column properties that affect signal propagation. Edge processing algorithms analyze noise floors locally, filtering out the constant hum of legitimate port operations and biological transients.
Actionable Insights
The system correlates acoustic anomalies with surface data to identify "dark vessels"—small craft not transmitting AIS that may be deploying swimmers. By analyzing environmental data, the system predicts acoustic shadow zones where thermal layers might hide threats, adjusting detection thresholds dynamically. It distinguishes the distinct acoustic footprint of Open Circuit Divers (bubbles) from the fainter mechanical signature of CCRs, providing high-fidelity classification.
Impact
Security operations centers receive high-confidence alerts rather than raw data streams, allowing watchstanders to maintain situational awareness without fatigue. When a confirmed threat is detected, the system calculates the intruder's track, enabling the precise vectoring of Maritime Safety and Security Teams (MSST) for interdiction. This capability transforms underwater security from a reactive guessing game into a proactive, data-driven defense posture aligned with escalating MARSEC levels.
Recommended Systems (2)
To achieve comprehensive protection, a dual-system architecture is recommended: a Perimeter Monitoring System to cover the harbor approach and channel, and a Point Defense System focused on high-value assets (piers, terminals, and anchored vessels).
System configuration image
System Overview
Purpose
Provides early warning of unauthorized underwater activity or dark vessels entering the harbor approach.
Deployment Context
Mounted on channel markers, buoys, or breakwater entrances at the edge of the port's jurisdictional zone.
Sensors
Required
Hydrophone
Captures acoustic signatures of small vessels, UUVs, and mechanical diver propulsion vehicles in the approach channel.
Important
Temperature
Essential for identifying thermal layers that create acoustic shadow zones, allowing operators to understand coverage gaps.
Camera
Verifies surface activity to correlate with acoustic contacts, confirming if a sound source is a legitimate vessel or a potential threat.