The sea is no longer just a transport route or an economic resource, but the centre of a silent yet crucial strategic contest. Today, the underwater domain has become a key arena of hybrid warfare, where national security is increasingly linked to the protection of vital but largely unseen infrastructure.
Our everyday lives depend on the seabed: more than 99% of global data travels through submarine telecommunications cables, while the energy security of nations depends on gas pipelines and power interconnectors.
Disrupting this infrastructure could halt banking transactions worth billions of euros and cut off the energy supply of entire countries. This is why underwater defence has become a global market estimated at around €50 billion a year.
What is being built: the ecosystem and the drone revolution
The industry's response to these threats is no longer limited to the construction of traditional submarines. The focus has shifted to the development of non-conventional systems and dual-use technology, designed to serve both the civil sector, including the maintenance and laying of fibre-optic and power cables, and the military.
One of the companies operating in this market is the Fincantieri Underwater Hub, headed by chief executive Pierroberto Folgiero. The group is bringing together an integrated ecosystem of domestic companies focused on underwater technologies. The aim is twofold: to support the digital transition - with the number of fibre-optic cables expected to double over the next decade - and to protect critical infrastructure.
How the DEEP system works
One of the group's main projects is the DEEP system (Dynamic Ecosystem for Enhanced Performance), a solution for protecting critical infrastructure built around an integrated technological chain:
- Early Warning System: a first barrier of sensors placed on the seabed detects potential threats by monitoring activity in the surrounding water column.
- Swarms of autonomous drones: once a threat is detected, the system deploys a group of small underwater drones.
- On-board Artificial Intelligence: the drones move towards the threat and, through sensors and an Artificial Intelligence algorithm, identify the type of danger in real time, allowing the immediate activation of risk-mitigation measures.
Why it is being built: the opacity of hybrid warfare
Geopolitical blocs no longer face off only in the open. New forms of warfare often rely on sabotage or other forms of pressure to target critical infrastructure.
Recent incidents, such as the attempted sabotage of the tanker SeaJewel off the coast of Savona - suspected of being part of Russia's shadow fleet - have accelerated the realisation that commercial ports and maritime corridors are sensitive targets that require protection.
This opacity of threats makes constant monitoring indispensable. States and private operators can no longer simply react once damage has occurred, which could lead to major digital or energy disruptions. Instead, they must anticipate risks by integrating seabed monitoring systems with surface drones that patrol inland waters and port access channels.
The new frontiers of defence: quantum sensors and underwater wireless networks
Emerging technologies are pushing the boundaries of underwater defence into areas that until recently belonged to science fiction.
- Internet cables become listening devices: one of the most innovative developments is DAS (Distributed Acoustic Sensing). This technique makes it possible to measure microscopic variations in tension inside standard fibre-optic cables used for web traffic, turning transoceanic cables into large underwater listening devices capable of detecting submarines or divers across vast areas.
- Quantum magnetometers: to overcome the limits of acoustic sonar in crowded waters, defence researchers are turning to quantum physics. New quantum magnetometers mounted on drones can detect minute changes in the Earth's magnetic field caused by the steel hull of a submarine tens of kilometres away.
- Interoperability and underwater wireless communications: as highlighted by the National Hub for the Underwater Dimension, the key challenge for 2026 and 2027 is the creation of common European standards to enable wireless, real-time communication between surface drones, seabed sensors and underwater drones from different countries, turning defence into a shared maritime awareness network aligned with NATO.
Towards digital decoupling?
Geopolitical risk is also pushing towards scenarios in which infrastructure becomes more fragmented. While Western countries are strengthening cables in the Mediterranean and Atlantic, China is promoting alternative digital infrastructure corridors in Asia and Africa.
The future of the underwater domain may not only be military. It could also see the emergence of two separate digital ecosystems, geographically divided along the ocean floor and protected by swarms of drones ready to defend the invisible borders of underwater cyberspace.
