A broken cable on the ocean floor slowed the internet for a whole country

Friday, October 2, 2026. All over the Philippines, people noticed the same thing: the internet was slow. Videos buffered. Pages took their time. Calls stuttered.

It was not their routers. It was not their ISP throttling them. It was a broken cable lying on the bottom of the sea.

By that evening, the advisories were out. Converge, PADECO, even the network help desk at UP Diliman, all warned subscribers about the same thing: the submarine cable segments connecting the Philippines to Singapore and Hong Kong were down. The country's Department of Information and Communications Technology said it was investigating the cause. Sabotage was on the list of possibilities, but officials said it was far too early to draw conclusions.

And then this quiet detail from PLDT, one of the country's biggest carriers: it had lost about 300 gigabits per second of capacity, and it had more than enough spare elsewhere to cover the loss.

That one sentence contains almost the entire story of how the internet actually works. Let me unpack it.

The internet is a maritime business

Here is the fact that surprises almost everyone: when your data travels to another continent, it almost certainly goes through the ocean. Submarine cables carry over 99 percent of all intercontinental data traffic, according to TeleGeography, the research firm that maps them. Satellites handle a tiny fraction. They always have.

There are nearly 700 cable systems down there, with about 1,900 spots where they come ashore. Each cable is roughly as thick as a garden hose. Inside are strands of glass, thinner than a human hair, and data travels through them as pulses of light. Small devices called repeaters, spaced along the cable, boost the signal so it survives the thousands of kilometers between continents.

And these cables break. A lot. Roughly 150 to 200 times a year worldwide. The cause is usually mundane: a ship's anchor dragging across the seabed, a fishing trawler's gear snagging a line, an earthquake, or plain equipment failure. The ocean floor is crowded and violent.

So why is the internet not breaking every week? Because it was built assuming this would happen.

Why these two cables mattered

Singapore and Hong Kong are not random dots on the map. They are two of Asia's biggest internet intersections. Networks from all over the region meet there to exchange traffic, because it is cheaper and faster to hand data to a neighbor than to send it the long way around. Engineers call these meeting points hubs, and the practice of exchanging traffic there is called peering.

A lot of the Philippines' traffic to the rest of the world normally passes through those two hubs. When the segments to both went down at once, it was like losing two major interchanges on the same day.

Why the internet got slow instead of dying

Here is the key question: if the cables broke, why did anything work at all?

Because the internet does not trust any single road. Philippine ISPs lease capacity on many cable systems heading in different directions: toward Hong Kong, Japan, Guam, the US west coast. When two paths died, traffic moved to the rest.

Every network on the internet constantly tells its neighbors which routes are alive. The system they use for this is called BGP, the Border Gateway Protocol. You can think of it as every intersection in the world posting live detour signs. A router in Manila says, "I can reach Singapore through this path." When the path dies, the announcement is withdrawn, the signs update everywhere within minutes, and traffic finds the next best route.

This is why slow, not dead. Picture a highway losing two lanes at rush hour. The same number of cars now squeezes through the lanes that remain. That is congestion. And some of the surviving routes are physically longer: instead of Manila to Singapore to its destination, a packet might travel Manila to Tokyo to the US west coast and back. Light is fast, but distance still counts. The delay has a name every backend engineer knows: latency. A few hundred extra milliseconds is the difference between a snappy call and a buffering one.

Globe, one of the country's big carriers, announced it was rerouting data traffic. That sentence is the press-release version of "we updated the detour signs."

A simplified sketch of what happened:

Manila ====== Singapore ====== rest of the world     X  broken
Manila ====== Hong Kong  ===== rest of the world     X  broken
Manila ====== Tokyo ====== rest of the world            longer, congested

Same cars. Fewer lanes. Longer detours.

How they find the break

This is my favorite part. When a cable snaps, the operator does not send a diver. They send a pulse of light down the fiber and listen for the echo.

It works like sonar. A break in the glass reflects a tiny bit of the light back. By measuring how long the echo takes to return, engineers can pinpoint the break to within meters, from a control room thousands of kilometers away. The tool has a fancy name, an optical time-domain reflectometer, but the idea is ancient: shout into a canyon, time the echo, know the distance.

Then a cable ship sails to the spot. It drags a grappling hook, or sends down an underwater robot, to haul the cable up from the seabed. Technicians splice in a new section of fiber, seal it, and drop it back down. It takes days to weeks, depending on weather and how far the nearest ship is. There are only about two dozen of these ships on standby around the world.

And while the ship is sailing, the internet just routes around the hole. You feel it as slowness. Your video call has no idea why. All it knows is that the road got longer.

What "300 gigabits of capacity" actually means

Back to PLDT's quiet sentence. ISPs do not own most of these cables. They buy capacity: slices of a cable's total throughput, like an airline buying seats on a route it does not own. Three hundred gigabits per second is roughly the room for tens of thousands of simultaneous video streams. Losing it is a real hit.

The second half of the sentence is the interesting part: "we have more than enough to cover it." That is redundancy, and it is the most boring and most important word in infrastructure. PLDT had paid for spare capacity on other routes, every day, for years, for exactly this moment. Redundancy is insurance you buy daily and are grateful for on the worst day.

The takeaway

The internet feels like weather, something in the air. It is not. It is glass tubes on the ocean floor, a small fleet of repair ships, and routers swapping detour signs with each other thousands of times a second.

Every time your connection slows and nobody can tell you why, remember the Philippines on October 2. Somewhere under the sea, possibly, a ship's anchor did it.

Here is a small experiment for this week. Run traceroute (or mtr on Linux, tracert on Windows) against a site you use every day and read the city names in the hops. The journey is more literal than you think. What is the strangest route your packets have ever taken? Tell me in the comments.