Three explosions were detonated on major gas lines between Russia and Europe earlier this autumn.

NATO says it will enhance its military presence in the Baltic Sea after Russia was accused of sabotaging Estonia's main power link.

And some experts say this could be the Kremlin showing it can attack critical infrastructure.

Putin's aggression does not stop in Ukraine.

Russian spy ships menace our waters.

And communications to Shetland have been severely disrupted after a subsea cable was damaged.

It's like somebody has flipped a switch and taken us back 20 or 30 years.

It's vast, deep, dark, cold, seemingly silent.

But the seabed hosts the arteries of the modern economy.

Telecom cables carrying terabytes of data, electricity grid connections and cables linking wind turbines.

Pipelines bringing oil and gas ashore or pumping it between countries to keep our home fires burning.

This huge network sits on the ocean

floor quietly working away with the majority of the population unaware of just how much is

happening under the waves. These assets are so valuable and strategically important to modern

life, the seabed has become the battleground for a new type of warfare. I'm Douglas Fraser,

and for the documentary from the BBC World Service, this is the Subsea War.

There is an estimated 10 trillion on financial transactions going through the scales each single day.

Katergina Zisk is a professor at the Norwegian Institute for Defence Studies in Oslo.

She highlights, among many other targets, the potential for cutting transatlantic telecom cables,

many of them linking North America through Irish waters and the Western approaches to the rest of Europe.

Again, we are talking about 99% of the world's data traveling transmitted through this

global network. So we are talking about financial information. It's not only about, you know,

...