Forget transparent seas – What’s the plan to deal with crowded oceans?

Well before then, Australia’s waters (our large exclusive economic zone and the entrances to Australia’s ports) and the strategically important choke points in our northern approaches, whose importance was recently reaffirmed by the Defence Strategic Review, are likely to have welcomed a new kind of visitor — small autonomous underwater vessels that will come in various shapes, sizes, and configurations. And that’s a visitor of the worst kind: one that outstays its welcome and moves in for good.

We can expect the People’s Liberation Army’s Navy (the PLA-N) and various Chinese civilian companies working with the PLA to be the proud owner-operators of many of these.

We won’t be able to claim any of this is a surprise.

The Chinese military has been developing and testing unmanned underwater and surface vessels for over a decade. Even public events like arms expos have been used by Chinese defence companies to showcase their products — like China State Shipbuilding Corporation’s Haishen 6000, a mid-sized UUV with an operating depth of up to 6,000 metres — well beyond the crush depth of manned submarines. The annual military parade in Beijing back in 2019 featured trucks carrying China’s HSU001 underwater drones. And “bionic drones” designed to look and swim like manta rays have been tested by the Chinese in the South China Sea. These are a tiny set of examples from the catalogue of known Chinese UUV programs.

It’s not all a one-way street, and it’s not as if Australians aren’t growing our own understanding of what’s possible right now and what will be possible in the next few years with continued development.

Australian defence companies have been developing their own uncrewed small surface and underwater vessels for our military to use, and the Australian Navy has been getting demonstrations of them for years now in Jervis Bay at Exercise Autonomous Warrior.

Companies like Ocius have developed small, long-range uncrewed surface vessels like the Bluebottle, able to carry modular payloads of up to 600 kilograms, tow sonar arrays, and stay at sea without the limitations of feeding and housing a crew. C2 Robotics has taken the underwater path, with its Speartooth large unmanned underwater vessel.

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These are existing technologies and designs. They show us two things: that large numbers of these small, affordable systems will be invaluable to Australia’s own military if it is to have that “impactful projection” the government wants it to build. And we need to plan and prepare now to be able to find, assess, and deal with potential adversaries’ swarms of these type of surface and undersea military systems.

Finding a static sea mine anchored to the sea floor is difficult. Clearing dumb sea mines from around ports and choke points is still almost as hard as it was back in World War Two. But finding hundreds — or thousands — of small, stealthy, mobile UUVs each carrying an explosive equivalent of a large sea mine is an exponentially more difficult task.

A cleared port entrance can become uncleared fast as swarms of smart UUVs and mines simply relocate to repair the minefield.

Think of the embarrassment caused to the US military by a single Chinese spy balloon floating over the American homeland for days before being brought down, combined with the brazenness of the Chinese government that sent it. Now look forward to 2026 and revelations that two, 10 or 129 mysterious small underwater vessels have been found floating around our waters or even in our ports — with Chinese authorities claiming that they are either not theirs or simply conducting civilian ocean research.

Even one being found anywhere near HMAS Stirling, where Australian Collins submarines operate from now and where the US Navy will be forward deploying Virginia Class nuclear submarines later this decade will be a strategically disturbing event — because if a UUV can get here with a sensor payload, it can also get here with a kinetic one.

The best, stealthiest, and deadliest sub-hunting nuclear submarines will simply not be the capability we need to deal with this threat of a crowded, hostile ocean.

So, even if the sub hunting and shipkilling roles of our AUKUS submarines remain important, we need to begin to plan and to act to deal with the nearer term and arguably more difficult problems presented by a persistent threat from large numbers of small, stealthy, armed and unarmed underwater vessels operating in our near region and wherever our Navy wants to be. We need to have both a defensive set of capabilities to find, understand, and deal with adversary unmanned underwater systems, along with our own offensive UUV systems.

Our US allies are already well into thinking this problem through and seeing the need to address critical vulnerabilities between now and 2027, as shown by the Special Competitive Studies group’s Offset-X report released in May 2023.

The underwater threat is linked to the rapidly emerging competition around use of AI-enhanced semi-autonomous and autonomous systems and something even more disturbingly real — the need to develop counter-AI capabilities to undercut and confuse adversaries employing AI and autonomy.

As the Howe royal commission into the bombing of Darwin in 1942 found, when military authorities know of an absolutely foreseeable and credible threat and fail to take adequate actions to deal with it, their failure risks Australian lives and security. And the post-event inquiries are scathing of individuals and institutions.

A crowded hostile ocean is not just foreseeable, it is close to being a reality. That, more than the risk of oceans becoming transparent, is what must focus the minds of our naval planners. It should also be a core part of the work of the review of the Australian Navy that Admiral William Hilarides is conducting right now for the government.

Deputy Prime Minister Richard Marles has told us that his Strategic Review is part of a “complete transformation of Australia’s standing in the world” and that it is a profound change in our strategic posture. The top two of five tasks he has clearly articulated for the Defence Force are: to defend our continent and our neighbourhood, and to deter through denial any adversaries’ attempt to project power against Australia or our interests through our northern approaches.

Making this real when it comes to our maritime security will take putting the sense of crisis and urgency in the government’s words into Defence Department action to accelerate the development and delivery of new capabilities in the immediate future.

It may take some Australian taxpayer treasure being spent on the small, the cheap, and the many in the undersea world, well before the $60 billion that’s going out the door between now and 2033 on nuclear subs is all spent.

Michael Shoebridge is director of Strategic Analysis Australia. From 2018 until September 2022, he was the director of the Defence, Strategy and National Security Program at the Australian Strategic Policy Institute (ASPI) in Canberra.