A new generation of AI-powered seafloor sensor networks has changed what submarine detection looks like. The question now is whether Southeast Asia is paying attention — because China already is.
The System That Watched the Cold War’s Oceans
For most of the Cold War, the West’s ability to track Soviet submarines depended on one of the most ambitious undersea engineering projects ever undertaken. The Sound Surveillance System — known as SOSUS — was a vast network of hydrophone arrays laid across the Atlantic and Pacific ocean floors, connected by undersea cables to shore-based processing stations. Classified, expensive, and extraordinarily effective, it was built on a simple principle: sound travels far underwater, and if you listen carefully enough from the right places, you can hear a submarine from hundreds of kilometres away.
When a Soviet submarine departed the Barents Sea and slipped through the Greenland–Iceland–UK (GIUK) gap into the North Atlantic, American analysts at their shore stations frequently knew about it before the submarine’s own crew had settled into their patrol routine. SOSUS was that good. [1]
That era is over. SOSUS has been largely retired from frontline submarine-hunting duty. Its operational successor — the Integrated Undersea Surveillance System (IUSS), formally renamed in 1985 — combines remnant fixed arrays with surface ships towing sonar and shore-based processing stations. [2] It was a system designed for a world where Russian and Chinese submarines were noisier, slower, and far fewer in number than they are today.
That world no longer exists. And into the gap, an American defence technology company has introduced something that may represent the most significant shift in undersea surveillance architecture in decades.
Enter Seabed Sentry
Unveiled in April 2025 by Anduril Industries, Seabed Sentry is not a single device. It is a distributed network of modular, cable-less sensor nodes designed to be placed on the ocean floor, where they sense, process, and communicate subsea data in real time — with no physical connection to the surface or shore. [3]
The nodes can be deployed autonomously by Anduril’s own Dive XL unmanned submarine, spread across a defined area to form a mesh network, and — critically — recovered, recharged, and redeployed. This last point matters enormously. Legacy systems like SOSUS were essentially permanent installations, their positions eventually mappable by any adversary patient enough to study cable routes and traffic patterns. Seabed Sentry nodes are mobile, unpredictable, and reconfigurable. If an adversary works out where they are, you move them. [4]
Key Specifications
| Specification | Detail |
|---|---|
| Endurance | Months to years per deployment |
| Depth rating | Exceeds 500 metres |
| Payload capacity | Over 0.5 cubic metres |
| Primary sensor | Ultra Maritime Sea Spear — extendable sonar array reaching approximately 10 metres |
| Software platform | Anduril Lattice (AI-driven sensor fusion) |
| Deployment vehicle | Anduril Dive XL extra-large autonomous underwater vehicle (XLUUV) |
| Design | Modular, open architecture — supports military and commercial payloads |
| Reusability | Fully recoverable; cleaned, recharged, redeployed |
Source: Anduril Industries product specifications, April 2025. [3]
The Sensor: Sea Spear
The acoustic sensor paired with Seabed Sentry was developed by Ultra Maritime under the name Sea Spear, and its design takes inspiration from the extendable booms used on satellites. Once a node is placed on the seafloor, the array extends outward to its full operational length, dramatically increasing its effective aperture and detection range. When it is time to recover the node, the array retracts, and the unit can be lifted by an autonomous vehicle — no human divers required. End-to-end in-water testing was completed in 2025. [5]
Anduril and Ultra Maritime have announced an exclusive partnership to integrate Sea Spear with Seabed Sentry as the primary sensing payload, combining Ultra Maritime’s AI-enabled acoustic processing with Anduril’s Lattice framework for real-time, distributed submarine detection. [6]
The Brain: Lattice AI
The intelligence layer running Seabed Sentry is Anduril’s Lattice software platform — the same AI system used across the company’s drone, surface vessel, and ground sensor products. Lattice fuses incoming acoustic data at the edge, meaning each individual node performs initial signal classification locally rather than forwarding raw audio to a distant shore station. Detections are communicated acoustically between nodes, and cueing data is surfaced to operators in real time. [3]
When a submarine is detected and tracked by multiple nodes simultaneously, Lattice triangulates its position. That cueing data can then be passed to response assets — maritime patrol aircraft, surface ships, or, in a wartime scenario, Anduril’s own Copperhead autonomous underwater weapon. [7]
Why It Matters Strategically
Unlike SOSUS, whose general layout could eventually be mapped by patient adversaries, Seabed Sentry’s mobile, cable-less design means its positions are never permanently known. The system is also designed for multinational use from the outset, with an open architecture that supports non-US sensor payloads and integration with allied command systems. [4]
Anduril has been explicit about what is driving demand. Russian Yasen-M class nuclear-guided missile submarines are among the quietest ever built, and China is rapidly expanding its submarine fleet. According to US Naval Intelligence testimony to Congress in March 2026, the People’s Liberation Army Navy (PLAN) could reach approximately 70 submarines by 2027 and roughly 80 by 2035, with an increasing proportion being nuclear-powered. [8] Between 2021 and 2025 alone, China launched 10 nuclear-powered submarines — more than the United States managed in the same period. [9]
This is the threat environment Seabed Sentry was designed for. And nowhere is that threat environment more immediately relevant than in Southeast Asia’s most critical waterway.
Why the Strait of Malacca Matters More Than You Think
The Strait of Malacca is not simply a busy shipping lane. It is, by most measures, the single most consequential chokepoint in the global maritime order.
Stretching approximately 900 kilometres between the Malay Peninsula and the Indonesian island of Sumatra, the strait narrows at its most critical point — the Phillips Channel near Singapore — to just 2.8 kilometres wide. [10] In 2024, a new record of 94,301 vessel transits was recorded — a 5.5 percent increase from the previous year. [11] By 2025, that figure had risen again, exceeding 102,525 transits — the first time the strait has seen more than 100,000 vessel passages in a single year, averaging 281 ship reports per day to the Klang Vessel Traffic Service alone. [12]
The economic weight of this traffic is staggering. As of 2024, over 35 percent of oil transported by sea and 20 percent of global gas flows pass through the Strait of Malacca. [10] It carries roughly one-quarter of all the world’s traded goods — more than the Suez and Panama Canals combined — and approximately USD 3.4 trillion in annual trade passes through it. [13]
For China specifically, the strait is an existential vulnerability. In 2003, then-President Hu Jintao coined the term the “Malacca Dilemma” to describe China’s dependence on this narrow corridor for energy supplies. With roughly 80 percent of China’s crude oil imports transiting the strait, any disruption — military, political, or accidental — would have immediate and severe consequences for the Chinese economy. [10]
The strait’s three littoral states — Malaysia, Indonesia, and Singapore — conduct coordinated surface patrols that have largely suppressed traditional piracy since the mid-2000s. Singapore hosts the Information Fusion Centre, a regional maritime intelligence hub with participation from more than 20 nations. These are genuine capabilities. They are, however, built almost entirely for surface and aerial threats. [14]
Beneath the waterline, there is almost nothing watching.
The Threat Already Taking Shape
This is where the picture becomes uncomfortable for Malaysia and its neighbours.
Since at least 2023, a fleet of Chinese research vessels — operating under the formal cover of oceanographic and climate science — has been conducting systematic seabed mapping operations across the Pacific, Indian, and Arctic oceans. The scale of this effort is extraordinary. Ship-tracking data reviewed by Reuters shows dozens of vessels travelling in the tight grid patterns characteristic of bathymetric survey work, not random scientific sampling. [15]
One vessel in particular — the Dong Fang Hong 3, operated by Ocean University of China — spent much of 2024 and 2025 surveying waters near Taiwan, around the US military hub of Guam, and across parts of the Indian Ocean. In October 2024, it reportedly inspected Chinese ocean sensors deployed near Japan and returned to the same location in May 2025. In March 2025, it conducted extensive survey tracks between Sri Lanka and Indonesia, covering maritime approaches to the Malacca Strait. [16]
The strategic purpose of this mapping campaign is not obscure to naval analysts. Submarines depend on detailed knowledge of undersea topography for three things: safe navigation, concealment using seabed terrain features, and predicting how sound propagates through the water column at different depths and temperatures — knowledge that determines both their ability to avoid detection and their ability to detect adversary submarines. [15]
China’s ambitions here go further than mere mapping. Chinese naval strategists have a formal name for what they are building: the “transparent ocean” — a concept first proposed in 2014 by Chinese oceanographer Wu Lixin that envisions a comprehensive sensor and data network capable of monitoring underwater movement across China’s strategic maritime zones. [17] According to US Office of Naval Intelligence Director Rear Admiral Mike Brookes, testifying to Congress in March 2026, this network already includes hundreds of fixed sensors deployed east of Japan, near the Philippines, and around Guam. [8] Chinese academic and government records also describe sensor arrays placed along the Ninety East Ridge — an undersea mountain chain in the Indian Ocean sitting near the approaches to the Malacca Strait. [17]
In plain terms: China is mapping the seafloor that matters most to it, planting sensors in waters through which its submarines will operate, and building the environmental intelligence needed to optimise those submarines’ performance in contested waters. The approaches to Malaysia’s shores are part of that programme.
Southeast Asian nations — the ones whose exclusive economic zones these activities increasingly touch — have no equivalent undersea awareness capability of their own. [18]
The Case for a Seabed Sentry-Type System in This Region
A policy paper published by the Center for Strategic and International Studies (CSIS) in September 2025 put the argument plainly: deploying seabed sensor arrays in critical straits — Malacca, Sunda, and the approaches to the South China Sea — is both feasible and strategically necessary. [18]
The paper drew explicit comparison to the US–Japan “Fish Hook Undersea Defense Line” — a seabed sensor network combining fixed arrays, satellite integration, and data fusion to monitor submarine movements across the Western Pacific. That system, the authors noted, demonstrates what regional cooperation and persistent undersea surveillance can achieve, and it could serve as a direct template for Southeast Asia. [18]
The Geographical Case
The narrow geometry of the Malacca Strait is, paradoxically, an asset for undersea surveillance. At its southern chokepoint, a submarine transiting the strait has very limited room to manoeuvre laterally. Even a modest network of distributed sensor nodes placed at the northern approaches — where the strait widens toward the Andaman Sea and deeper water — could create overlapping acoustic coverage across all viable submarine transit lanes.
The Sunda Strait (between Java and Sumatra) and the Lombok Strait (between Bali and Lombok) also require attention. Both are alternative routes for vessels wishing to bypass Malacca, and any serious undersea domain awareness architecture for Southeast Asia would need to cover all three chokepoints. [10]
The Commercial Case
The security case does not stand alone. The Malacca Strait and its flanks are home to critical undersea cable infrastructure carrying the majority of internet and data traffic between Asia and Europe. They are flanked by offshore energy infrastructure — pipelines and platforms — whose vulnerability to sabotage was demonstrated globally by the Nord Stream pipeline attacks in September 2022. [4]
A seabed sensor network deployed in this region would not need to be purely military in character. Its data would have immediate value for:
- Port security — tracking unauthorised underwater activity near port approaches and anchorage areas
- Critical infrastructure protection — monitoring undersea cables and pipelines for tampering or sabotage
- Pattern-of-life mapping — establishing baseline profiles of normal underwater activity to detect anomalies
- UUV tracking — monitoring the growing number of unidentified unmanned underwater vehicles appearing in regional waters
This dual-use character is potentially important for the political feasibility of any deployment in a region where direct military framing can trigger diplomatic complications. [18]
Malaysia’s Current Posture — And Its Gaps
Malaysia has increased its defence budget consistently in recent years. The 2025 defence allocation was RM21.2 billion (approximately USD 4.9 billion) — about 8 percent higher than the previous year. [19] The 2026 budget increased further to RM21.7 billion (approximately USD 5.15 billion), with Defence Minister Mohamed Khaled Nordin explicitly linking the increase to South China Sea operations. [20]
Planned acquisitions under these budgets include medium, short, and very-short-range air defence systems, two Multi-Role Support Ships (MRSS), maritime surveillance aircraft for the Malaysian Maritime Enforcement Agency (MMEA), and new-generation patrol vessels. [21] These are welcome modernisation steps. They are, however, focused almost entirely on surface and aerial capabilities.
Defence analysts have been direct about what this means in practice. Thomas Daniel, a Senior Fellow at the Institute of Strategic and International Studies Malaysia, noted that without credible deterrence capability, Malaysia has “reduced options and ability to protect our interests.” [22] The sinking of the fast attack vessel KD Pendekar in August 2024 — after a navigational error caused it to strike a reef, with the ageing hull accelerating flooding — brought the state of Malaysia’s naval fleet into sharp public focus. Investigators found approximately RM384.5 million in losses from more than 1.62 million spare parts no longer compatible with the navy’s existing vessels. [22]
The undersea domain, meanwhile, receives virtually no dedicated attention in published defence planning documents. There are no publicly known hydroacoustic sensor arrays in Malaysian waters. There is no equivalent to Japan’s contribution to the Fish Hook network. The Royal Malaysian Navy’s two Scorpène-class submarines — KD Tun Abdul Razak and KD Tun Razak — are capable platforms for offensive undersea operations, but two submarines cannot provide persistent wide-area surveillance of a 900-kilometre strait and its alternate bypass routes.
According to the Asia Maritime Transparency Initiative, at least one Chinese coast guard vessel operated in Malaysian waters every single day between 1 January and 27 September 2024. In early September 2024, three Chinese naval vessels reportedly entered Malaysia’s exclusive economic zone off Sarawak, loitering near an offshore oil rig. [23] This is the surface picture. The undersea picture is unknown — because Malaysia currently has no way to see it.
The Politics Are Harder Than the Technology
None of this is straightforward to implement, and it would be misleading to suggest otherwise.
Malaysia’s longstanding strategic neutrality posture — carefully maintained across multiple administrations and embedded in ASEAN’s non-interference doctrine — creates genuine political complications around hosting or operating what is, at its core, a US-origin military technology with obvious anti-China applications. Any government in Kuala Lumpur that openly partnered with an American defence contractor for submarine detection would face immediate and sustained diplomatic pressure from Beijing. Indonesia faces similar constraints, compounded by a military culture that has historically resisted deep foreign intelligence integration.
Singapore is the most natural anchor for any regional undersea awareness network. It already operates the Information Fusion Centre, its navy is among the most capable in Southeast Asia relative to its size, and it has a long record of hosting sensitive multilateral maritime intelligence arrangements without the political volatility that complicates arrangements with larger neighbours. The practical model for any near-term deployment would likely involve Singapore as the data fusion hub, with sensor nodes placed cooperatively in Indonesian and Malaysian waters through bilateral technical arrangements structured to keep the military character of the deployment discreet. [18]
AUKUS Pillar II — the technology-sharing pillar of the Australia–UK–US trilateral agreement — already explicitly includes non-AUKUS partner nations in capability sharing, with several Southeast Asian countries identified as potential beneficiaries. This creates a plausible delivery pathway that does not require Malaysia or Indonesia to sign a direct bilateral defence agreement with an American company. Framed as regional infrastructure protection rather than anti-submarine warfare — which is an accurate description of much of what such a network would do — a sensor deployment could potentially attract the multilateral political support that makes it sustainable over time. [18]
Indonesia’s “major defence cooperation partnership” with the United States, established in April 2026, and Malaysia’s critical minerals MoU signed with the US in October 2025, both suggest that the regional political ground is shifting — if incrementally — toward frameworks that allow deeper security cooperation without requiring formal alliance commitments. [24]
The Window Is Narrowing
The most urgent consideration is timing.
China’s seabed mapping campaign is not preliminary survey work. It is the intelligence preparation for operational deployment. The sensors it has already placed near Japan, around the Taiwan Strait, and across Indian Ocean approach routes represent the early stages of an undersea surveillance architecture that — within a decade — could give the PLAN a detailed, real-time picture of submarine activity across its entire strategic perimeter. [16]
Once that picture is established and the data accumulated, any attempt by Southeast Asian nations to develop a countervailing capability will be starting from behind in waters that China already understands more thoroughly than they do. The acoustic signatures, thermal layers, salinity profiles, and seabed topography of the Malacca approaches are being catalogued right now by Chinese research vessels. The window to establish a baseline of independent regional undersea awareness — before China’s picture becomes dominant — is open, but it is not open indefinitely. [15]
Malaysia’s defence planning has taken meaningful steps forward in recent budgets. But the RM21.7 billion allocated for 2026, while the largest defence allocation in the country’s history, represents approximately 1.2 percent of GDP — below the 1.5 percent target the Defence White Paper set for 2030, and well below the spending levels of neighbours who face comparable maritime challenges. [25] Critically, virtually none of it addresses the undersea domain.
What the Seabed Sentry Model Offers
The Cold War comparison is instructive but deliberately incomplete. SOSUS was a product of its era — fixed, massively expensive, ultimately mappable, and wholly owned and operated by one nation. Seabed Sentry represents something genuinely different:
- Distributed and mobile — no fixed positions to map and exploit
- AI-enabled at the edge — processing happens on the node, not at a distant shore station
- Modular and open — supports non-US payloads and allied integration
- Reusable and recoverable — dramatically lower operational costs than legacy fixed arrays
- Designed for allied deployment — Anduril is already in active discussions with European navies and explicitly pitching Seabed Sentry for multinational chokepoint defence [7]
The Strait of Malacca, the Sunda Strait, and the Lombok Strait are among the most strategically important bodies of water on earth. They are also, beneath the surface, almost entirely unwatched by the three nations legally responsible for their security.
That asymmetry — between their global importance and the near-total absence of undersea domain awareness among Malaysia, Indonesia, and Singapore — is not a gap that will close by itself.
China is not waiting for Southeast Asia to figure this out. The mapping is already underway. The sensors are already going in. The question is whether the nations whose sovereignty, trade, and critical infrastructure depend on these waters will act before the underwater picture is drawn entirely by someone else.
Key Terms Explained
Hydrophone — An underwater microphone designed to detect and record sound waves travelling through water. The basic building block of passive sonar systems like SOSUS and Seabed Sentry.
Passive sonar — A detection system that listens for sounds made by a target (such as a submarine’s engines or propellers) without emitting any signal of its own. Because it transmits nothing, it is very difficult to detect.
Acoustic signature — The unique pattern of sounds produced by a specific vessel type or submarine class. Like a fingerprint — experienced analysts and AI systems can identify submarine classes from their acoustic signatures alone.
Bathymetric mapping — Detailed measurement and mapping of the shape and depth of the ocean floor. Essential for submarine navigation, concealment planning, and predicting how sound travels underwater.
GIUK Gap — The Greenland–Iceland–UK gap. A strategic maritime chokepoint in the North Atlantic that Soviet and Russian submarines must transit to reach the open ocean. The Atlantic strategic equivalent of the Malacca Strait.
XLUUV — Extra-Large Unmanned Underwater Vehicle. A large, fully autonomous submarine capable of operating without a crew and deploying payloads such as Seabed Sentry sensor nodes.
AUKUS — The trilateral security partnership between Australia, the United Kingdom, and the United States, announced in 2021. Pillar I covers nuclear-powered submarine acquisition for Australia. Pillar II covers advanced capability sharing — including undersea surveillance technologies — with potential extension to partner nations in the Indo-Pacific.
PLAN — People’s Liberation Army Navy. The naval arm of China’s armed forces, currently the largest navy in the world by total number of vessels.
Malacca Dilemma — A term coined by Chinese President Hu Jintao in 2003 to describe China’s strategic vulnerability arising from its heavy dependence on the Strait of Malacca for energy imports. Roughly 80 percent of China’s crude oil transits this single chokepoint.
Sources and References
- Federation of American Scientists — Integrated Undersea Surveillance System (IUSS). Available at: irp.fas.org/program/collect/iuss.htm
- Wikipedia — SOSUS (Sound Surveillance System). Last updated March 2026. Available at: en.wikipedia.org/wiki/SOSUS
- Anduril Industries — Anduril Introduces Seabed Sentry Undersea Sensor Network, April 3, 2025. Available at: anduril.com/news/anduril-introduces-seabed-sentry
- The War Zone (TWZ) — Submarine Surveillance System That’s Rapidly Deployable, Unpredictable Unveiled By Anduril, April 3, 2025. Available at: twz.com
- The Washington Times — Anduril Announces New AI-Powered Underwater Sensor Network, April 3, 2025. Available at: washingtontimes.com
- PR Newswire / Ultra Maritime — Anduril and Ultra Maritime Announce Exclusive Partnership on Groundbreaking Autonomous Ocean Sensing Capability, April 7, 2025. Available at: prnewswire.com
- Naval News — Anduril Expands Across Europe With Next-Gen Anti-Submarine and Infrastructure Defense Solutions, August 1, 2025. Available at: navalnews.com
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- National Security Journal — China Launched 10 Nuclear Submarines in 4 Years — The U.S. Built 7 in the Same Period and Can’t Match Beijing’s Pace, May 2026. Available at: nationalsecurityjournal.org
- Wikipedia — Strait of Malacca. Last updated May 2026. Available at: en.wikipedia.org/wiki/Strait_of_Malacca
- Informare / Nippon Maritime Center — New Annual Record for the Transit of Ships in the Straits of Malacca and Singapore, January 9, 2025. Available at: informare.it
- Seatrade Maritime News — Malacca Strait Vessel Traffic at Record Levels in 2025, April 2026. Available at: seatrade-maritime.com
- ShipsTrack — Strait of Malacca: World’s Busiest Shipping Lane. Available at: shipstrack.com
- Observer Research Foundation — South-First Connectivity: The Malacca Strait’s Strategic Role, September 26, 2025. Available at: orfonline.org
- Interesting Engineering — China Mapping Ocean Bed for Submarine War, March 25, 2026. Available at: interestingengineering.com
- Army Recognition — China Deploys 42 Ships and Hundreds of Oceanic Sensors to Prepare for Submarine Warfare Against the US Navy, March 30, 2026. Available at: armyrecognition.com
- Eurasian Times — Guam, Hawaii & Malacca — China’s Research Ships Silently Map Strategic Waters for Submarine Edge Over U.S.?, March 25, 2026. Available at: eurasiantimes.com
- Center for Strategic and International Studies (CSIS) — Closing the Undersea Surveillance Gap in Southeast Asia, New Perspectives on Asia, September 11, 2025. Available at: csis.org
- ISIS Malaysia — Are Malaysia’s Forces Underfunded? Navy Ship Sinking Spotlights Defence Spending, November 2024. Available at: isis.org.my
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- New Straits Times — MMEA: 2026 Budget Reinforces Malaysia’s Maritime Defence Readiness, October 10, 2025. Available at: nst.com.my
- ISIS Malaysia — Are Malaysia’s Forces Underfunded? Navy Ship Sinking Spotlights Defence Spending, November 2024. Available at: isis.org.my
- Free Malaysia Today — RM21bil Defence Budget Not Enough Amid Rising Threats, Ageing Assets, Govt Told, October 22, 2024. Available at: freemalaysiatoday.com
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