The next front in Ukraine’s war is beneath the sea, and Britain is dangerously vulnerable

Surrounded by water and protected by a formidable navy, initially prioritised under Elizabeth I, the British Isles have long been notoriously difficult to attack.

Nowadays, what was an advantage now creates a huge vulnerability. In the digital age, it is no longer armies or fleets that connect Britain with the world, but cables and pipelines laid quietly across the seabed. Today, that dependence is its most glaring, and arguably at its most precarious.

When we think about modern warfare, we picture tanks crossing borders, missiles striking cities, or troops mobilising en masse. What we can’t comprehend is the battlefields that are less tangible, in cyberspace and particularly beneath the sea. It is this domain that poses one of the most serious threats to the UK’s national security.

Almost everything that keeps Britain functioning depends on undersea infrastructure. Around 99 per cent of global internet traffic travels through around 60 undersea cables laid across the ocean floor. Vast networks of pipelines deliver oil and gas that heat our homes and power our economy. These systems are the hidden arteries of modern life, and they are dangerously exposed.

At the start of this year, reports emerged that Russia is building an underwater drone fleet designed to target precisely this kind of infrastructure. They are autonomous, stealthy systems capable of operating thousands of metres below the surface, far from public view and often beyond the reach of traditional naval patrols.

If such a capability were ever deployed against the UK, it is no secret that the scale of the consequences would be astronomical. Financial transactions could be almost completely halted, internet and power outages across the country and, needless to say, mass panic across the isles. All of this could happen without a single missile fired or soldier deployed on land.

The other main weapon used by those that employ these tactics is deniability. Anchors can drag, equipment can fail, sabotage can be dismissed as an “accident,” allowing attackers to hide under the guise of plausible deniability and delaying political response. In modern conflict, that grey zone is the exact strategy pursued by hostile states.

We are already seeing worrying signs. Late last year, Russian vessels were detected probing UK waters close to critical undersea infrastructure. More recently, a Russian “shadow fleet” oil tanker dropped anchor just miles off the Scottish coast, days after being seized in a US-led operation with British military support. These incidents are not random, they are tests of NATO awareness, response times, and resolve and we are lagging behind.

Much of the world’s attention is rightly focused on the brutal land war being fought in Ukraine. But warfare has changed. Conflict now spans domains that are invisible, autonomous, and difficult to regulate. Under the sea, there are no fences or checkpoints, only cables and pipelines quietly doing their job, assumed to be safe because they always have been. That assumption simply no longer holds. Defensive measures lag dangerously behind, fragmented across government departments, regulators, and private operators.

Unfortunately, undersea security currently sits between defence policy, energy security, and digital infrastructure. This means that whilst the threat continues to grow, responsibility is not attributed.

Britain needs to treat undersea infrastructure as a core pillar of national security. What this involves is a coherent national strategy, sustained investment, and close collaboration between government, defence, and the companies that build and operate these systems. The cost of prevention is tiny compared to the economic and social cost of recovery after a successful attack.

Autonomous Underwater Vehicles (AUVs) like GREYSHARK, are a key way in which this capability gap can be addressed. Around the clock surveillance fundamentally enhances awareness in areas with little human presence and urgent response requirements, allowing for continuous monitoring and the collection of high-quality data with minimal human intervention. This also allows clear attribution, holding bad actors accountable, and enabling retaliatory measures. AUVs can also be trained to take action against an enemy and eliminate these threats.

For Great Britain, ignoring the most vulnerable part of its critical infrastructure simply because it lies out of sight would be a profound mistake. The next war will not begin with explosions we can hear or an invasion we can see. It will start quietly, beneath the waves, with a severed cable and a nation suddenly cut off from the outside world. If we wait until that moment to take this threat seriously, it will already be too late.

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Eugen Ciemnyjewski is the CEO of EUROATLAS (euroatlas.com), a firm building autonomous undersea drones to protect subsea internet and energy infrastructure.

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