FIELD GUIDE · Tracking & Intel
How Submarine Cables Carry the Internet Across the Oceans
How does the internet actually cross an ocean?
Ask most people how the internet crosses an ocean and they'll say "satellites." It's one of the most widespread misconceptions about modern infrastructure. The reality is far more physical: almost all international internet traffic travels through fibre-optic cables lying on the floor of the sea — a hidden web of glass strands wrapping the planet. The live cable map plots them, and once you understand what you're looking at, it's one of the most quietly astonishing layers there is.
Glass threads under the sea
A submarine cable is, at heart, a bundle of optical fibres — each finer than a human hair — carrying data as pulses of light. Across the open ocean the whole cable is only about as thick as a garden hose. That slender package is wrapped in steel wire for strength, a copper conductor to deliver power, and waterproof insulation. Every 50 to 100 kilometres sits a repeater, powered through that copper, boosting the light signal so it can survive a journey of thousands of kilometres without fading.
Laid end to end, the world's cables stretch well over a million kilometres. They are the genuine backbone of the global internet — not a backup to satellites, but the main event. Satellites carry a tiny fraction of international traffic; cables carry the rest, with far more capacity and far less delay.
Where cable meets land
Follow any cable to a coastline and you reach a landing station — the building where the undersea line connects to the terrestrial network. On the map these are the nodes where the glowing lines touch shore. They matter out of all proportion to their size: a single landing station can be the funnel through which a whole region's data enters and leaves. That concentration is what makes both cables and their landing points strategic chokepoints, and why a map of them is as much an intelligence picture as a technical one.
Why cables break — and why you rarely notice
Cables break more often than most people would guess — but the network is built to shrug it off. The leading causes are mundane: ships' anchors and fishing trawlers dragging across the seabed account for most faults, with undersea landslides and earthquakes adding the rest. When a cable does fail, traffic reroutes automatically through other cables in seconds, thanks to a deliberately meshed, redundant network.
Trouble appears in two situations. The first is dependence: a region served by only one or two cables has no fallback, so a single fault can mean real outages. The second is multiple simultaneous failures, which is why cable damage near geopolitical flashpoints draws such scrutiny — and why this layer pairs naturally with the GPS jamming layer and global incidents in the map's Infrastructure at Risk fusion. Repairs are physical and slow: a specialised ship sails out, grapples the cable up from the seabed, and splices it by hand, a process that can take days to weeks.
Reading the map
What the cable layer gives you is a sense of the internet's true geography — which routes the world's data actually follows, where it bottlenecks, and which coastlines and chokepoints carry the heaviest load. Switch it on and trace a cable from one continent to another; every line is a real, named system carrying a slice of global traffic across the dark of the deep ocean. It reframes a daily abstraction — "the internet" — as something with a physical map, a set of vulnerable pinch points, and a quiet, constant maintenance effort keeping the world connected.
Frequently asked questions
Does the internet really run through undersea cables, not satellites?
Yes — the overwhelming majority of international internet traffic, well over 95%, travels through fibre-optic cables lying on the ocean floor, not through satellites. Cables carry vastly more data with far less delay than satellites can. Satellite links (including newer low-orbit constellations) matter for remote areas and backup, but the backbone of the global internet is physical cable on the seabed.
How thick is a submarine cable?
Surprisingly thin — across most of the deep ocean, a cable is about the diameter of a garden hose. The optical fibres at the core are finer than a human hair; the rest is protective layers of steel wire, copper (to power the signal repeaters), and waterproof insulation. Near shore, where the risk of damage is higher, cables are armoured more heavily and often buried beneath the seabed.
What happens if a cable is cut?
Usually, very little that users notice — because traffic is automatically rerouted through other cables within seconds. The global network is meshed with built-in redundancy for exactly this reason. Problems arise when a region depends on only one or two cables, or when several are damaged at once: then you can see slowdowns or outages until repair ships physically retrieve the cable from the seabed and splice it, which can take days or weeks.
What damages undersea cables?
Most cable faults are accidental and mundane: ships' anchors dragging across the seabed and fishing trawlers are the leading causes, along with occasional undersea landslides or earthquakes. Deliberate sabotage is rare but receives outsized attention because of its strategic implications — which is why cable damage near geopolitical flashpoints draws scrutiny. The routine reality is that cables break fairly often and are quietly repaired.
What is a cable landing station?
It's the facility on the coast where an undersea cable comes ashore and connects to the land-based network. These landing points are strategically important chokepoints — a handful of buildings where continents' worth of data funnels in and out. On the map they're the nodes where the cable lines meet the coastline.
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