How the Internet Crosses Oceans — The World's Submarine Cables

Picture the floor of the Atlantic. Two and a half miles down, in permanent darkness and near-freezing water, lies a cable about as thick as a garden hose. Inside it, wrapped in steel wire and copper and a waterproof sheath, are a few strands of glass fibre no wider than a human hair. Down those strands, as pulses of light, travels a large share of everything moving between Europe and the Americas: the web, video streams, bank transfers, the contents of the cloud.

There are around 700 cables like it on the world's seabeds, and together they are the real, physical internet between continents. This guide is about the shape of that network — how it's laid out, where it gathers into dangerous bottlenecks, and where it touches land — and how it connects to the rest of the Grid. For how the cables themselves actually carry data, see the companion piece on how submarine cables carry the internet.

A planet wired under the sea

The numbers are hard to picture. This map holds 714 cables totalling roughly 1.8 million kilometres — enough to circle the planet about forty-five times. They carry, by most estimates, well over 95% of all international data traffic. The satellites overhead, including the newer low-orbit constellations, matter for ships, aircraft, remote areas and resilience — but for the bulk movement of data between continents, almost everything is down here, on the bottom of the sea.

The systems range wildly in size. At one end are short domestic hops — a few kilometres linking two islands or crossing a strait. At the other are the intercontinental giants: 2Africa, which loops around the whole of Africa and into Europe and Asia at close to 40,000 km; new Meta-led systems reaching five continents; the long-running SeaMeWe family stitching Southeast Asia to the Middle East and Western Europe. A handful of cables, each costing hundreds of millions of dollars, carry a remarkable share of the world's connectivity.

Why the sea, and not the sky

It's a fair question why, in an age of satellites, the world's data crawls along the seabed at all. The answer is capacity and speed.

A single modern cable can carry hundreds of terabits per second — vastly more than any satellite link. And light through a cable travels a shorter, more direct path than a signal bounced up to orbit and back, so the delay is far lower. That matters for everything from a smooth video call to a financial trade where milliseconds are money. Per bit of data moved, a seabed cable is also dramatically cheaper.

So the division of labour is clear: satellites reach the places cables can't — the middle of an ocean, a plane in flight, a remote valley — while the cables do the heavy lifting of moving the planet's data in bulk. The map you're reading is that heavy-lifting layer.

Where the cables run — and where they bunch up

Cables don't spread evenly across the oceans. They follow the routes between the places that generate and consume the most data, and they cluster along the cheapest, safest paths — which means the network has chokepoints, stretches where many cables run close together and a lot of the world's traffic is concentrated into a narrow corridor.

A few are worth knowing:

• The North Atlantic, between the north-eastern United States and north-western Europe, is the busiest cable corridor on Earth — the data spine between two of the world's largest economies.
• The Red Sea and the Suez approaches form the great pinch point between Europe and Asia. A huge share of Europe–Asia traffic threads through this narrow body of water; faults here have disrupted connectivity across whole regions.
• The Luzon Strait, between Taiwan and the Philippines, is the gateway for cables crossing the Pacific into East Asia — a seismically active stretch where earthquakes have severed multiple cables at once.
• The Singapore and Malacca region is where the cables of Southeast Asia, the Indian Ocean and the Pacific converge — one of the densest landing clusters anywhere.

These bottlenecks are the network's real vulnerability. Any one cable can be cut and the traffic simply reroutes; but where dozens run through the same corridor, a single earthquake, a dragging anchor in a busy shipping lane, or a cluster of faults can strain an entire region's connectivity at once. It's the same lesson as the energy chokepoints the world's oil and gas squeeze through — concentration is efficient, and concentration is fragile.

Where the cables come ashore

A cable is only useful where it surfaces. Each one ends at a landing point — a spot on a beach where the cable is buried under the sand and run to a building just inland, where its traffic is handed to the land networks that carry it onward.

This map shows 1,914 landing points across 186 countries and territories, and they cluster exactly where you'd expect the world's traffic to flow: the eastern seaboards of the United States and Canada, the United Kingdom as the great gateway between North America and Europe, and the dense archipelago crossroads of Indonesia, the Philippines and Japan. Zoom into any major coastline on the live map and the radar-green dots bloom — each one a place where the undersea internet becomes the internet on land.

One thing worth noticing: unlike the land-grid layers on this canvas — the transmission lines, substations and pipelines, which all follow where volunteers have mapped the most — this cable and landing data is genuinely global. The picture of the undersea network is about as complete as public mapping gets.

How it ties into the rest of the grid

This is the Grid canvas — "the world, wired" — and the submarine cables are half of that story. The land grid moves energy across continents: power stations, the high-voltage lines that carry their output, the switchyards where those lines meet. The cables move data across oceans. Between them, they are the two great planetary networks that keep the modern world running.

And they meet at the data centres. A hyperscale data centre is useless in isolation: it needs vast amounts of electricity coming in over the power grid, and it needs to be connected to the rest of the world's data — which, for anything intercontinental, means a submarine cable. It's no accident that the biggest operators of data centres have become major builders and owners of cables: they are wiring their own facilities directly into the seabed network. Switch on Data Centres and Submarine Cables together and you can see the shape of it — the places where the world's compute sits, and the strands that connect them across the oceans.

An honest map

A few caveats, in keeping with how everything here is built.

This is a dated snapshot, not a live feed. Cables are announced, laid and retired continually, so the network shown is the one captured on the date noted on the hub page, drawn from TeleGeography's public map. Each cable's length is a great-circle estimate computed from its mapped route — a real figure, good for ranking the giants and labelling each cable, but not an official engineering measurement, and not used to draw one cable thicker than another (a cable's capacity, which would be the meaningful thing, simply isn't in the public data — and a short cable can carry enormous traffic). A couple of planned cables whose shore landing isn't fixed yet have their undecided landing points left off.

So read this as what it is: an honest, well-sourced map of the publicly known undersea network — the cables that carry the world's data between continents, and the coasts where they come ashore — rather than a complete or official register.

Open the live Grid map, switch on Submarine Cables, and zoom to a coastline: the glowing lines reaching out across the sea, and the green dots where the internet climbs out of the ocean and onto land.