L3Harris Technologies tested its Rock Lobster deployable underwater acoustic communication relay alongside U.S. Navy capabilities during Exercise Rim of the Pacific (RIMPAC) 2026 off Hawaii, as part of an AUKUS Pillar II undersea warfare activity, the company announced on October 19, 2026. The Australian-developed relay operated with Australia’s Lightfish uncrewed surface vessel (USV), built by San Diego-based Seasats, to demonstrate interoperability between Australian and U.S. underwater acoustic communications technologies.
RIMPAC 2026, the world’s largest international maritime exercise, ran off Hawaii from June 24 to July 31, 2026; Australia’s Department of Defence put participation at 34 nations and more than 25,000 personnel. Within the exercise, personnel from the Royal Australian Navy, DSTG and the U.S. Navy tested AUKUS Pillar II subsea and seabed warfare capabilities in mission scenarios focused on protecting critical undersea infrastructure, with Australian uncrewed vehicles operating from the Australian Defence Vessel (ADV) Guidance. The work builds on earlier testing through the Maritime Big Play experimentation series, which AUKUS partners use to accelerate interoperability between uncrewed maritime systems. Pillar II is the advanced capabilities track of the Australia, United Kingdom and United States partnership.
How the Rock Lobster Acoustic Relay Bridges Allied Undersea Networks
Passing command-and-control data beneath the surface remains one of the most persistent problems in naval operations. Radio waves attenuate rapidly in seawater, leaving acoustic links as the primary means of reaching submerged platforms, and those links suffer from low bandwidth, multipath propagation and shifting sound speed profiles. The challenge grows as navies field uncrewed underwater vehicles (UUVs) that must receive tasking without surfacing.
Rock Lobster is designed to close part of that gap as a deployable and disposable relay node. Developed by the L3Harris Maritime team in Australia with the Royal Australian Navy (RAN) and the Defence Science and Technology Group (DSTG), the system relays acoustic messages to and from underwater systems and seabed assets. Its disposable design means relay nodes do not need to be recovered.
The relay has a documented test record. During Exercise Autonomous Warrior 2023 in Jervis Bay, New South Wales, DSTG reported that Rock Lobster relayed mission-relevant information originating in the United States to an underwater system in the bay. It has since been refined through the AUKUS Maritime Innovation Challenge and the Maritime Big Play series. L3Harris has also fitted an acoustic modem to an Ocius Bluebottle USV to communicate with seabed assets through the Rock Lobster relay.
The work draws on L3 Nautronix, now part of L3Harris, which developed the Hydro Acoustic Information Link (HAIL) used aboard Collins-class submarines. Key Rock Lobster parameters remain undisclosed: L3Harris has not published the system’s frequency band, data rate, transmission range, operating depth, endurance or supported waveform standards, including compatibility with the NATO JANUS digital underwater communications standard.
Lightfish USV Integration and the AUKUS Pillar II Uncrewed Agenda
At RIMPAC 2026, Rock Lobster worked with Lightfish, a solar-electric USV that falls within the U.S. Navy’s very small USV class. Seasats describes a self-righting hull roughly 11 feet long, endurance of up to six months or 8,000 nautical miles, operation up to sea state 6 and GPS-denied navigation, with a modular payload bay rated at up to 66 pounds. The vessel can be launched by hand by one or two people.
Those parameters define the role: a persistent, low-profile gateway between acoustic networks below and satellite links above. Paired with a seabed relay, it forms a surface-to-seabed chain that could extend command and control to UUVs while reducing reliance on a crewed ship on station. Lightfish already carries U.S. program credentials: in October 2025, the U.S. Navy awarded Seasats a Small Business Innovation Research (SBIR) Phase III indefinite-delivery/indefinite-quantity contract with a reported ceiling of $89 million to supply Lightfish to the U.S. Marine Corps through 2032 if all options are exercised.
The industrial relationship predates the exercise. L3Harris made a strategic investment in Seasats in October 2022, and venture capital firm Shield Capital led Seasats’ $10 million funding round in early 2025. L3Harris frames the Seasats tie as part of a strategic partnership with Shield Capital aimed at moving emerging defense and commercial technologies to operational users faster.
“Interoperability doesn’t happen by accident,” said Nino DiCosmo, President, Maritime, Space & Mission Systems, L3Harris. “It takes years of collaboration, testing and refinement with our partners. RIMPAC 2026 is a reflection of that work and a strong signal of where AUKUS undersea capability is headed.”
Analysis: The RIMPAC result matters less for any single system than for what it reveals about Pillar II’s approach to the undersea fight. Acoustic interoperability is a prerequisite for the shared UUV operations and seabed infrastructure protection missions the AUKUS partners are rehearsing together. An expendable relay that can be paired with a hand-launchable USV shifts undersea networking away from fixed, costly infrastructure toward attritable nodes seeded ahead of operations. The caveat is that RIMPAC is a cooperative environment; performance against acoustic jamming, the detectability of relay transmissions and link security have not been publicly addressed.
L3Harris has not announced a production contract, RAN acquisition program or delivery timeline for Rock Lobster, which remains in the experimentation phase, and the United Kingdom’s role in this specific activity was not detailed. Further Maritime Big Play and Autonomous Warrior iterations will indicate whether the relay transitions to a program of record. L3Harris operates 15 locations in Australia with more than 550 employees, 30% of whom have served in the Australian Defence Force.