Iran’s cable threats test an aging repair fleet

As negotiations continue over ending the U.S. and Israel’s war with Iran, pressure around the Strait of Hormuz has shifted toward undersea fiber-optic cables. But the biggest vulnerability isn’t the cables themselves—it’s the small, aging fleet of specialized

By the time a damaged undersea cable is found, the clock is already running. Crews have to retrieve it. splice in a replacement section. test the line. and lay it back down—often with a ship holding position for days. The work can’t always wait. and in the Persian Gulf that urgency collides with a simple reality: only one repair vessel is currently inside the region.

Iran’s cable threats arrive at a moment when the undersea network is built to reroute around routine failures. but its repair system has far less slack. While U.S. and Israel negotiations over ending their war with Iran continue. Iranian officials and state-linked media floated plans in May to impose fees on fiber-optic cables beneath the Strait of Hormuz and to hand Iranian firms control over their maintenance and repair.

The cables beneath the strait matter, but not in the way many headlines imply. TeleGeography, a telecom research firm, estimates the region carries less than 1 percent of global international bandwidth. Yet even when the overall network can reroute. the question becomes what happens when damage occurs and repair ships can’t reach the site quickly—or in sufficient numbers.

Industry investment has surged. The industry now sees about $4 billion to $5 billion in annual investment. close to double what it was a decade ago. driven by a building boom in new cables. But the gap is in the capacity that keeps those cables alive. “We have a lack of investment in the maintenance ship fleet. ” says Mike Constable of the consulting firm Infra-Analytics and the SMART Cables initiative. He likens the situation to buying an expensive Mercedes without insurance: “It’s a huge investment going in. but there’s very little investment. almost zero. in protecting it.”.

Constable also points to an imbalance in how the fleet is used. In the Pacific, he says, a couple repair ships perform just two repairs a year and otherwise sit on standby, while other regions face heavier demand.

The network depends on a global fleet of around 60 specialized vessels that lay and maintain the world’s cables. and fewer than 20 dedicated solely to repair. Each year, cable operators log some 150 to 200 faults. The International Cable Protection Committee estimates 70 to 80 percent of those faults arise from accidents involving fishing equipment and ships’ anchors.

Replacing a damaged segment sounds simple on paper—crews locate and retrieve the cable with a remotely operated vehicle. splice in a replacement section. test the line. and lay it back down. In practice, the method often forces a ship to linger near the problem. That can mean days at sea, potentially near a conflict zone.

And the fleet itself is getting older. A recent TeleGeography study co-authored by Constable finds that about half the vessels in the global cable fleet. and nearly two thirds of those in the maintenance fleet. will reach the end of their service life by 2040. Many ships added in recent years are not new; they’re secondhand vessels converted from other sectors. including construction ships from the oil and gas industry. The study also estimates that about a quarter of the world’s existing cable kilometers will be due for retirement by 2030.

At the same time, more cable is heading toward riskier waters. More than a million kilometers of new cables are slated for the southwest Pacific Ocean and parts of the Atlantic, including dozens of new cable routes in and near the Middle East.

Repairs. meanwhile. tend to cluster where the ocean is difficult and the human traffic is dense—not where politics most often fixates. Constable says many repairs occur in Southeast Asia. especially in the South China Sea. with shallow waters crowded with fishing boats and trawlers. Undersea mudslides can also damage cables, and future seabed mining could eventually add another hazard. “If it’s high-risk, go around it,” he says.

Even getting to a repair site can be slow. Sheryl Ong. head of Asia at Global Marine. a U.K.-based company with its own fleet of cable ships. describes how permitting can stall operations. Securing a government’s sign-off to enter its territorial waters can take a month or more. “Sometimes permitting takes a long time before we can actually get out to sea and get things done,” she says.

Security concerns have been building for several years. especially since Russia’s invasion of Ukraine in 2022 and the Nord Stream gas pipeline sabotage later that year. Cable disruptions in the Baltic Sea followed, and the Red Sea delivered a sharper lesson. In 2024, a commercial vessel struck by Houthi militants severed multiple cables as it sank. Repairs were delayed for months while companies and governments worked out whether it was safe and lawful to enter the area.

Some operators bury lines in shallow water to add protection, but the coverage isn’t absolute. An anchor dragging through sediment can still damage a cable, Constable says. In the Strait of Hormuz, cables are clustered closely together. That clustering cuts both ways: Iran might deliberately disrupt connectivity in Kuwait. Qatar. or Saudi Arabia by attacking cables serving those countries. But the risk is that such moves could also harm cables carrying data for Iran’s own networks.

For Constable, that’s part of why the most vulnerable targets are increasingly on land rather than beneath the waves. Cable landing stations along the coast are exposed to drone attacks in a way that undersea cables are not. In that logic, Iran could target those stations without necessarily risking its own connections.

The story of the undersea Internet, then, isn’t only about geopolitics reaching the seafloor. It’s about a repair system that has to respond in tight windows. often far from home ports. with vessels that are approaching the end of their working lives just as new cables multiply the places they will need to be fixed.

Iran Strait of Hormuz undersea cables fiber-optic cable repair ships TeleGeography SMART Cables International Cable Protection Committee Persian Gulf Mike Constable Sheryl Ong Global Marine South China Sea cable security drones cable landing stations