China's New Deep-Sea Cable Cutter and its Security Implications
Abigail Darwish | 3 April 2025
Summary
China unveiled a device capable of severing underwater cables at depths of up to 4,000 metres, making the cables increasingly vulnerable.
The technology has significant military, economic, and political implications, increasing the potential for communication disruptions and the undermining of financial systems through the targeting of critical undersea cables.
China’s growing underwater capabilities significantly heighten the security risks for geopolitically contentious regions like Taiwan and the South China Sea, as well as strategic sites like Naval Base Guam.
China unveiled a device capable of severing deep-sea underwater cables, raising significant security concerns. Developed by the China Ship Scientific Research Centre and the State Key Laboratory of Deep-sea Manned Vehicles, the tool is engineered to operate at depths of up to 4,000 metres (13,123 feet)–twice the maximum range of existing subsea communication infrastructure. This expanded range eliminates the depth-based security buffer, making previously unreachable cables vulnerable to sabotage.
The device features a 6-inch diamond-coated grinding wheel that spins at 1,600 rpm (rotations per minute), enabling it to slice through armoured cables. The titanium alloy shell and oil-compensated seals overcome operational limitations, allowing it to withstand the immense pressure at extreme ocean depths, remaining fully functional under forces equivalent to 400 times the atmospheric pressure. As well, its use of advanced robotic arms and precise positioning technology help mitigate the challenge of low visibility in deep-sea environments by enabling remote operation and accurate cable alignment.
Whilst the device is intended to be used for commercial purposes, specifically in Chinese crewed and uncrewed submersibles, its capabilities provide significant political, economic, and military implications. Undersea cables are the backbone of global communication and data transfer, carrying over 95% of international internet traffic. These cables are essential for financial transactions, government communications, and everyday digital services, making them crucial to both economic stability and national security. As geopolitical competition intensifies, undersea cables have become strategic assets, with major powers seeking to control, protect, or disrupt these networks.
Critically, the technology developed by China might be leveraged against adversaries such as Taiwan–which has already reported at least four cases of cable malfunctions this year. Beijing’s new cable cutter could advance “grey zone” tactics aimed at isolating and pressuring Taiwan, potentially serving as a precursor to military action. Alternatively, Beijing could blockade Taiwan, by severing the cables, as a means of political pressure. This is concerning particularly given maritime tensions escalating evidenced by increased military posturing and recent incidents such as China’s use of “shadow fleet” tactics where Taiwan’s government seized a Togo-flagged cargo ship in February, crewed by Chinese workers, amidst the recent string of cable damages. Similarly, in December, a Belize-flagged Russian general cargo vessel was also loitering off the coast of Taiwan. The use of deep-sea cable cutters is not an isolated incident but a part of hybrid operations. Russia likewise engages in cable disruptions in the Baltic Sea, and has employed shadow fleets there also to carry out these operations.
Adding to China’s repertoire as the operator of the largest fleet of crewed and uncrewed submersibles globally, it also recently announced an initiative to construct a 2,000-metre deep “space station” in the South China Sea, further highlighting its expanding underwater capabilities. China’s growing capabilities also implicate the security of the region more widely with strategic points, including Naval Base Guam–central to the US military’s Indo-Pacific strategy–becoming increasingly vulnerable given that the island hosts over a dozen civilian and defence fibre-optic cables.
In an era where underwater networks are crucial to global communications and data distribution, the development of such disruptive technologies represents a turning point that could potentially reshape the regional geopolitical strategies of major powers, particularly those of the US and its allies, and heighten the risks of maritime conflict.
Forecast
Short-term (Now - 3 months)
It is highly likely that China will continue to disrupt cable networks in the South China Sea.
It is likely that Russia will continue to use “shadow fleet" in the region, with Beijing-Moscow relations likely to remain close amidst the growing Washington-Moscow ties.
It is likely that there will be international diplomatic pressure on China, as well as Russia, to cease disruptive activities, such as the sabotage of undersea cables and the use of shadow fleet, especially if there is an uptake in this malicious activity with China’s new capabilities.
Medium-term (3-12 months)
It is highly likely that China will continue to disrupt cable networks in the South China Sea.
Long-term (>1 year)
It is likely that, over time, the growing strategic importance of underwater cables could spark an arms race for advanced submersible technologies capable of disrupting these networks, creating a new frontier for technological espionage.
It is likely that mechanisms to fortify cable security will be developed, should cable disruption significantly increase, especially in geopolitically significant regions like the South China Sea.
