Two publications this week address the same subject from different angles: the International Institute for Strategic Studies on submarine cables in the Indo-Pacific, and an ASEAN-focused paper on strengthening subsea cable resilience in Southeast Asia.

Submarine cables carry the overwhelming majority of international internet traffic. Satellites carry a small fraction. Nearly everything you do online that crosses a border travels through a bundle of glass fibres lying on the seabed.

How fragile they actually are

A deep-sea cable is roughly the diameter of a garden hose. Near shore, where damage is most likely, it is armoured and thicker.

Cables break often — the global figure runs to well over a hundred faults a year. The overwhelming majority are accidental: ships dragging anchors, trawlers, submarine landslides, earthquakes. Most of the world never notices, because traffic reroutes automatically through other cables.

That redundancy is the whole of the resilience story. A country with many cable landings barely registers a break. A country served by one or two loses a large share of its international connectivity, and stays that way until a repair ship arrives.

Why repair is the bottleneck

Fixing a cable requires a specialised repair vessel, which must locate the fault, grapple the cable from the seabed, lift it, splice in new section and lower it back.

There are not many such ships in the world, the fleet is ageing, and they are unevenly distributed. A fault in a region without a nearby vessel waits for one to sail, sometimes for weeks. Permits to work in another state’s waters can add further delay.

Cable industry bodies have warned for years about repair capacity, and it is the least glamorous and most consequential part of the problem. Building a new cable is a commercial decision that attracts investment. Maintaining a fleet of repair ships is a cost nobody wants to carry.

Why Southeast Asia in particular

Geography concentrates the risk. Cables between Europe, the Middle East and East Asia funnel through a small number of maritime chokepoints, and the waters around Southeast Asia are shallow, busy with shipping, prone to earthquakes and in places disputed.

The disputed part matters for a specific practical reason. Laying and repairing cables requires permits from coastal states, and where sovereignty over an area is contested, obtaining them becomes a political question rather than an administrative one. Routes are increasingly planned to avoid contested waters, which makes them longer and more expensive.

The same waters are the subject of the dispute we report on separately today.

Accident or sabotage

Deliberate damage to cables has moved up the agenda following incidents in the Baltic and elsewhere, and this is where careful reading matters.

Distinguishing sabotage from an accident is genuinely hard. A dragged anchor produces similar damage whether the dragging was careless or intentional, and proving intent requires evidence about a vessel’s conduct that is often unavailable. Several incidents initially reported as suspicious have ended without a definitive finding.

That uncertainty cuts both ways. It means claims of sabotage should be treated cautiously — and it also means a state wishing to damage a cable has plausible deniability built in, which is part of what makes the tactic attractive.

The resilience response is the same either way: more cables, more diverse routes, more landing points, and more repair ships. None of that depends on attributing any particular break.

Sources

• International Institute for Strategic Studies, New geographies: submarine cables in the Indo-Pacific, 10 September 2026, via ISEAS Daily News on Southeast Asia
• Strengthening Subsea Cables Resilience in Southeast Asia: The Way Forward for ASEAN, listed in the same digest
• International Cable Protection Committee material on fault causes and repair capacity
• United Nations Convention on the Law of the Sea, provisions on submarine cables and coastal state permissions