Does China have the ability to cut deep-sea cables?

According to research reports, Chinese research institutions have obtained patents for deep-sea cutting equipment that can sever cables in deep water far from any normal fishing need, widening the room for “pretend accident” operations.

Threats to Submarine Cables: Shadow Fleets & Gray-Zone Sabotage

Q: What is the biggest threat to submarine cables?

Statistically, 41% of faults come from fishing trawls and 16% from anchors, mostly accidental; but deliberate gray-zone sabotage is the hardest to attribute and is the core concern this site monitors.

Q: How can you tell an accident from deliberate sabotage?

Deliberate sabotage is often disguised as an accident — using civilian fishing or cargo ships, acting late at night or in deep water, and switching off AIS beforehand to make it hard to distinguish from a genuine accident.

Q: What is a “shadow fleet”?

Vessels with unclear or frequently changed flags, complex ownership structures, and anomalous AIS records. Originally used to evade Russian oil sanctions, they have recently also appeared near submarine cables.

SERIES → 01 Submarine Cable 02 AIS 03 Taiwan Status 04 Threats 05 Enforcement 06 Methodology

About 100 to 200 submarine cable outages occur globally every year. Most happen in places you've never heard of, most are repaired within weeks, and most go unnoticed.

But "most" isn't "all." Some cable cuts are deliberate. And in Taiwan's surrounding waters, that line is becoming increasingly blurry.

100–200

global cable outages per year

41%

caused by fishing (trawl snagging)

16%

caused by ship anchors

0.13%

of ocean area near Taiwan — disproportionate incident share

Three Layers of Threat

Threats to cables fall into three distinct categories, each with different detection difficulty and response requirements.

Layer 1: Natural Threats

The ocean itself is a cable's first enemy. Submarine earthquakes can simultaneously sever multiple cables in seconds; turbidity currents triggered by underwater landslides can sweep through cable paths; corrosion and biological damage cause long-term natural wear. These threats cannot be prevented — only mitigated through route design to avoid high-risk geological zones and by building sufficient redundancy.

Layer 2: Accidental Damage

Fishing trawl nets (41%) and ship anchors (16%) account for the largest share of cable damage. Large bottom trawls can reach 500 meters deep, easily snagging shallow-water cables; the impact of heavy anchors from large cargo ships can cut through cable armor. Most such incidents are accidental, not deliberate — but when they occur frequently in sensitive waters, the "accident" explanation warrants careful scrutiny.

Layer 3: Deliberate Sabotage (Gray Zone Attacks)

This is the core threat this site monitors. Deliberate saboteurs intentionally disguise their actions as "accidents" to avoid accountability — using fishing boats or cargo vessels rather than warships, choosing deep-water areas where real-time evidence is impossible, and disabling AIS before acting. Because it's indistinguishable from "accident," this becomes a perfect gray zone tactic.

Natural Threats in Reality: The 2006 Hengchun Earthquake

On the morning of December 26, 2006, a magnitude 7.0 earthquake struck offshore Hengchun. The resulting submarine landslides simultaneously severed 7 international submarine cables passing through Taiwan's southern waters within hours.

2006 Hengchun Earthquake Impact

Severe disruption to international telephone and internet between Taiwan, Hong Kong, and Southeast Asia
Transpacific communications from mainland China, Japan, and South Korea affected
Some financial markets experienced trading interruptions
The last damaged cable wasn't repaired until February 2007 — nearly 49 days in total
Multiple global cable repair ships deployed simultaneously still required this long

This event clearly demonstrated the systemic impact of "multiple simultaneous cable breaks," and warned of the dangers of insufficient cable redundancy.

Shadow Fleets: The Perfect Tool for Gray Zone Attacks

In recent years, a sprawling network known as the "Shadow Fleet" has emerged into international view. These vessels share common characteristics: unclear or frequently-changed flagging, complex ownership structures (multiple shell companies), anomalous AIS records, and appearing in sensitive waters with no explicable operational purpose.

Initially, shadow fleets were primarily used for Russian oil sanctions evasion — since the 2022 Russia-Ukraine war, hundreds of tankers have circumvented Western sanctions this way. But security analysts began noticing the same fleet appearing near submarine cables around Taiwan, the Baltic Sea, and elsewhere, with behavioral patterns inconsistent with normal sailing or fishing operations.

The critical turning point: When a cargo vessel of unclear nationality appears for no apparent reason over a submarine cable route at 3am, loiters at low speed, then disables AIS, and the next morning the cable is cut — can we still call this an "accident"?

Recent Major Incidents Timeline

2023 Feb

Matsu Double-Cut Incident

On Feb 2 and 8, two Chinese fishing vessels (reportedly) severed both of Matsu's submarine cables (PCCS and MATSU-T). 14,000 Matsu residents lost internet for ~50 days. Taiwan was unable to prosecute the vessels under the "accident" framework.
2024 Nov

Yi Peng 3 Incident (Baltic Sea)

The Chinese vessel Yi Peng 3 sequentially severed the "C-Lion 1" cable connecting Finland and Germany, and a cable between Sweden and Lithuania in the Baltic Sea. Danish naval vessels blockaded the ship for 5 weeks; China refused to cooperate with the investigation. The incident placed NATO nations on high alert about cable vulnerability, and brought the pattern of "Chinese vessels severing cables" to widespread European media attention for the first time.
2025 Jan 11

Xing Shun 39

The Chinese bulk carrier Xing Shun 39 (MMSI: 412703070, flag: Tanzania) was operating in Taiwan's northeastern waters when it disabled AIS approximately 10 km from the TAW-US cable route, after which the cable was confirmed severed. Taiwan's Coast Guard arrived to find the vessel already gone. Subsequent investigation revealed the vessel was likely a Chinese shadow fleet member, with its actual owner concealed through multiple shell companies.
2025 Feb

Hong Tai 58

The Chinese bulk carrier Hong Tai 58 is suspected of severing another cable in waters north of Matsu. The pattern mirrored Xing Shun 39: the vessel quickly departed after the incident, and the investigation stalled in flag-state jurisdiction. Taiwan's government lodged a formal diplomatic protest, but the perpetrators remain unprosecuted.

Technical Escalation: Deep-Sea Cutting Capability

Analysts also point to a more alarming trend: China is developing active cutting technology targeting deep-sea cables. Traditional "accidental" methods mainly occur in shallow water (within 200 meters), because deep-sea cables are difficult to reach through normal fishing operations.

But according to research reports, Chinese naval research institutes have obtained patents for deep-sea operational equipment capable of cutting cables at greater depths — locations far from any plausible fishing or commercial sailing needs. This means the cover story of "pretending it's an accident" is expanding into deep-sea environments that previously offered almost no plausible deniability.

Why Is Deep Water Harder to Monitor? Deep-sea cable damage (>1000m) is difficult to detect via satellite and far harder to repair than shallow-water breaks. ROV operations at such depths are extremely expensive and time-consuming. Locating the exact break point on a deep-sea cable can take weeks, and repair may require 60+ days.

Why This Is the Perfect Gray Zone Tactic

Looking across these threats, a disturbing common logic emerges: submarine cables are targets with extremely high attack payoff and extremely difficult attribution.

Attacks occur on the deep seabed, with no witnesses
Civilian vessel disguise means no obvious "armed attack"
Fishing accident or anchor strike can be claimed as cover
Victim nations struggle to collect real-time evidence and lack legal means to prosecute
Effects can impose enormous pressure on a target country without triggering NATO Article 5 or UN Charter Article 51

This is exactly why Taiwan must build a proactive monitoring system rather than waiting to react after incidents occur. The next article explores Taiwan's existing enforcement framework, and the institutional challenges it faces.

Anchor Dragging vs Deliberate Sabotage: How to Tell Them Apart

Almost every cable-damage case hinges on the same question: was it an accidental anchor drag or deliberate sabotage? Because the physical result can be identical (an anchor dragging across the seabed and snagging a cable), "a cable broke" alone proves almost nothing about intent. Whether it is suspicious is hidden in the pattern of behavior.

✅ More like an accident

AIS was on and continuous through the event.
A plausible context: heavy weather, a dragging anchor, or mechanical failure.
Only one cable snagged, with no repeated passes.
The vessel cooperates afterward and can be contacted and investigated.

⚠️ More suspicious

AIS was switched off or spoofed before nearing the cable (going dark).
Abnormally slow, zigzag, or back-and-forth movement over the cable.
Multiple cables damaged in quick succession.
The vessel has identity changes, a flag of convenience, or a sanctions record.

No single indicator can "prove" intent — but when several red flags coincide, deniability erodes. That is the logic behind this site's threat scoring: not to rule on any one event, but to accumulate behavioral evidence and surface the few most worth investigating.

FAQ

What is the biggest source of cable threats?

Statistically 41% come from fishing trawls and 16% from anchors, mostly accidental — but deliberate gray zone sabotage is the hardest to attribute and the core of our monitoring.

How can you tell an accident from deliberate sabotage?

Deliberate sabotage is disguised as an accident — using civilian fishing or cargo vessels, acting at night or in deep water, and disabling AIS beforehand to blur the line.

What is a "shadow fleet"?

Vessels with unclear or frequently-changed flags, complex ownership, and anomalous AIS records — first used to evade Russian oil sanctions, and increasingly seen near submarine cables.

Does China have deep-sea cable-cutting capability?

According to research, Chinese institutes hold patents for deep-sea cutting equipment able to sever cables far from any plausible fishing need — expanding the "pretend it's an accident" playbook.

Sources

The concepts on this page can be verified against these public, authoritative sources:

This page is for research and education; detection signals are leads to investigate, not legal or factual findings. See the methodology.

🛰️ Taiwan Gray Zone & Submarine Cable Monitor

Threats to Submarine Cables