Almost every email, video call, and financial transaction that crosses an ocean travels not through satellites overhead but through a global web of fiber-optic cables lying on the seafloor, some no thicker than a garden hose. That system carries the overwhelming majority of the world’s international internet and telephone traffic, which means a single break in the wrong cable, whether caused by a dragging ship anchor, an underwater landslide, or deliberate sabotage, can measurably slow or sever connectivity for an entire country or region until repair crews can locate and fix the damage.
A Global Network Built on Surprisingly Fragile Cables
Submarine communications cables now stretch across every major ocean, bundling hair-thin glass fibers that carry data as pulses of light at close to the speed of light itself. Despite carrying trillions of dollars in daily financial transactions and the bulk of international data traffic, the cables themselves are physically modest, protected by layers of steel wire, copper, and plastic insulation that leave them roughly the diameter of a garden hose in the open ocean, though they are built considerably thicker and more heavily armored near coastlines where they are most exposed to damage.
Most of these cables are privately owned or jointly financed by consortiums of telecommunications companies and, increasingly, major technology firms that operate their own cloud and streaming services and want direct control over how their data crosses the ocean. Laying and maintaining this infrastructure requires specialized cable-laying ships and years of planning, since routes must account for ocean depth, seismic activity, and existing cables already occupying the seafloor.
Why Fishing Boats and Anchors Cause Most Cable Damage
The leading cause of submarine cable damage is not sabotage or natural disaster but ordinary maritime activity. Fishing trawlers dragging heavy nets along the seabed and ships that drop or drag anchors in shallow coastal waters account for a large share of reported faults each year, simply because so much of the cable network runs through the relatively shallow, heavily trafficked waters near ports and continental shelves. Even a slow-moving vessel dragging an anchor across the wrong stretch of seafloor can sever a cable carrying a meaningful share of a region’s internet capacity.
Natural events pose a smaller but more dramatic risk. Underwater landslides triggered by earthquakes have severed multiple cables at once in the past, since a single geological event can disturb cables bundled together along the same stretch of seafloor. A well documented earthquake off Taiwan in 2006 damaged several cables simultaneously and disrupted internet and phone service across large parts of East Asia for days while repair ships worked to locate and fix each break.
How a Break Actually Gets Repaired
Finding and fixing a submarine cable fault is a slow, highly specialized process. Repair ships use grappling equipment to locate the damaged section on the seafloor, sometimes at depths of several thousand meters, then haul the cable to the surface, cut out the damaged portion, and splice in a new segment before lowering the repaired cable back down. Depending on the cable’s location, water depth, and weather conditions, a single repair can take anywhere from several days to several weeks, during which any traffic that depended on that cable must be rerouted through other, often less direct paths.
Because specialized cable-repair ships are limited in number and shared across wide regions, a season with multiple simultaneous faults, whether from storms, fishing activity, or coincidence, can strain the available repair capacity and leave some breaks waiting longer than usual for a ship to become available. Maintenance agreements typically assign a small number of dedicated repair vessels to cover enormous stretches of ocean, which is part of why a cluster of unrelated faults in different parts of the world can create backlogs even when no single incident is especially severe.
Chokepoints Where Damage Hits Hardest
Not every part of the network carries equal risk if damaged. Certain narrow maritime corridors act as chokepoints where many separate cables run close together because of geography, meaning a single incident in that stretch of water can knock out several routes at once rather than just one. Regions where a large share of a country’s or even a continent’s international bandwidth funnels through a small number of cable landing points are especially vulnerable to a single localized event causing outsized disruption.
Waters such as the Red Sea and parts of the Baltic Sea illustrate the risk, since numerous cables connecting entire continents pass through relatively narrow, heavily trafficked corridors. In recent years, a series of incidents involving vessels dragging anchors across multiple cables in these congested waters has drawn heightened attention from European governments and military officials, who have raised concerns about how much of a region’s connectivity can hinge on a handful of vulnerable chokepoints.
Why Big Tech Companies Are Now Building Their Own Cables
Large technology companies that depend on moving enormous volumes of data between data centers on different continents have increasingly moved from simply leasing capacity on shared cables to financing and building their own private cable systems. Owning a cable outright gives a company more control over its route, its priority for repairs, and its long-term capacity planning, rather than sharing those decisions with a consortium of other operators. That shift has added new investment into the undersea cable industry even as the underlying vulnerability, a thin strand of glass and steel lying exposed on the ocean floor, remains fundamentally unchanged no matter who owns it.
Governments and telecommunications operators have increasingly pushed for greater route diversity and additional cable capacity specifically to reduce this concentration risk, since relying on just a few chokepoints leaves entire regions exposed to slowdowns whenever any one of those critical cables goes down, whether the cause turns out to be an anchor, an earthquake, or something more deliberate.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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