Almost All Intercontinental Internet Traffic Travels Underwater
Roughly 99 percent of intercontinental data traffic, including video calls, financial transactions, and web pages, physically crosses oceans through fiber-optic cables lying on the sea floor rather than bouncing off satellites in space.
Satellites carry less than one percent of this traffic. They matter for remote or hard-to-wire locations, but they are not the backbone of global internet connectivity.
The Concept Started With Telegraph Wires, Not Fiber Optics
Undersea cables predate the internet by well over a century. The first attempt at a transatlantic telegraph cable was laid in 1858, connecting Ireland and Newfoundland and allowing messages to cross the Atlantic in minutes instead of the roughly ten days a ship took.
That 1858 cable failed after only a few weeks of use due to insulation problems, but it proved the basic concept was possible.
A Durable Transatlantic Cable Followed in 1866
After several more failed or short-lived attempts through the 1860s, a reliable, long-lasting transatlantic telegraph cable was successfully completed in 1866, finally establishing dependable direct communication between Europe and North America.
This 1866 success set the template that undersea cable engineering has followed ever since: lay a protected conductor across the ocean floor, and route information along it faster than any surface transport ever could.
Fiber-Optic Cables Replaced Copper Starting in the Late 1980s
The first transatlantic fiber-optic cable, known as TAT-8, went into service in 1988, carrying data as pulses of light through glass fibers instead of electrical signals through copper, dramatically increasing how much information a single cable could carry.
This shift from copper to fiber optics is the technological foundation that made today's high-bandwidth global internet physically possible.
A Modern Cable Is Surprisingly Thin for Its Job
In the deep ocean, a modern submarine cable is often no thicker than a garden hose, containing a bundle of hair-thin glass fibers surrounded by layers of steel wire, copper, and insulation to protect against pressure and corrosion.
Closer to shore, in shallower water where fishing trawlers, anchors, and currents pose a much greater risk, the cable is wrapped in extra armor and can grow considerably thicker.
Specialized Ships Lay Cable at a Slow, Deliberate Pace
Purpose-built cable ships lay these lines by slowly unspooling cable from massive onboard tanks as they cross the ocean, often guided by a plow that buries the cable into the seabed in shallower coastal zones for extra protection.
Laying a major transoceanic cable system is a multi-month operation involving careful route surveys of the seafloor to avoid fault lines, shipwrecks, and other hazards beforehand.
Cables Get Damaged Regularly, and Repair Is Routine
Submarine cables are damaged somewhere in the world with real regularity, most often by fishing trawlers dragging equipment or ships dropping anchors in shallow coastal waters, far more frequently than by any dramatic deep-sea event.
A global fleet of specialized repair ships is kept on standby precisely for this reason, capable of locating a break, hauling the cable to the surface, splicing it, and redeploying it, often within days to a couple of weeks.
The 2Africa Cable Is the Longest Ever Built
The 2Africa cable, backed by Meta and a consortium of telecom operators, stretches roughly 45,000 kilometers, making it the longest submarine cable system in the world, longer than the Earth's circumference.
It connects 33 countries across Africa, Europe, and Asia, and was designed specifically to expand affordable, high-speed internet access to regions of Africa that had historically been underserved by existing cable routes.
Big Tech Companies Now Own or Co-Own Major Cable Routes
Companies like Meta, Google, Amazon, and Microsoft have moved from simply leasing capacity to directly funding and co-owning entire cable systems, reflecting how much of global internet traffic now originates from their own data centers and services.
This marks a real shift from the twentieth-century model, when undersea cables were built and owned almost exclusively by telecom carriers and national telephone companies.
TeleGeography Maps the World's Cable Network in Real Time
The Submarine Cable Map, maintained by the research firm TeleGeography, tracks essentially every active and planned undersea cable system worldwide, showing landing points, cable names, ownership, and route paths in an interactive public map.
It has become the standard public reference that journalists, researchers, and telecom professionals use when discussing how any two points on Earth are physically connected online.
There Are Well Over 500 Active Cable Systems Today
The global network now consists of several hundred separate cable systems, collectively spanning well over a million kilometers of cable across every ocean, connecting nearly every populated coastline on Earth.
New systems are added regularly, driven by rising demand for video streaming, cloud computing, and data-heavy applications that require ever more transoceanic bandwidth.
Cable Routes Follow Cost, Geography, and Politics All at Once
Choosing a cable's route is not simply the shortest line between two continents. Planners weigh underwater terrain, distance from fault lines and shipping lanes, landing station availability, and the political stability of countries along the way.
This is why some cables take longer, less direct paths, avoiding regions where regulatory hurdles, security concerns, or geological risk make a more direct route impractical.
A Single Break Can Disrupt Internet Access for an Entire Country
Countries connected to the global internet through only one or two cable systems are especially vulnerable. A single cable cut near their coast can slow or sever most of their international internet capacity until repairs are completed.
This risk has driven many governments and telecom operators to invest deliberately in multiple, geographically separated cable connections rather than relying on a single physical link to the rest of the world.
Cable Landing Stations Are the Hidden Chokepoints
Every undersea cable comes ashore at a specific landing station, a physical facility where the marine cable connects to terrestrial fiber networks. These stations are concentrated in a relatively small number of coastal hubs worldwide.
Because so much global traffic funnels through a limited set of these landing points, they represent both a technical chokepoint and a location of real strategic and security interest to governments.
Sharks Have Bitten Cables, but Fishing Gear Is the Bigger Threat
Shark bites on cables have been documented and did prompt some early cable-armoring research, but the far more common and significant source of cable damage worldwide comes from commercial fishing equipment and ship anchors, not marine wildlife.
Modern cables in shallow, high-traffic coastal waters are specifically armored and often buried to reduce this dominant, human-caused risk.
Latency, Not Just Capacity, Drives Cable Route Decisions
Financial trading firms and other latency-sensitive industries push for the most direct possible cable routes, since shaving even a few milliseconds off a transoceanic signal's travel time can matter enormously in high-frequency trading and similar applications.
This demand has occasionally justified building new, more direct cable systems even in corridors already well served by older, longer-routed cables.
Cables Cross Some of the Deepest, Most Remote Parts of the Ocean
Transoceanic cables often pass through water several kilometers deep, well beyond where sunlight reaches, resting on the seafloor in some of the most remote and least explored terrain on the planet.
Engineers must account for enormous water pressure, extreme cold, and near-total darkness when designing a cable meant to function reliably for twenty-five years or more without maintenance in the deep sections.
Repeaters Boost the Signal Every Few Dozen Kilometers
Light signals weaken as they travel through glass fiber over long distances, so cables include repeaters, sealed devices spaced roughly every 60 to 80 kilometers, that amplify the optical signal to keep data readable across thousands of kilometers.
These repeaters draw power sent down the cable itself from onshore stations, meaning a functioning cable also carries an electrical current alongside its optical data.
The Middle East Sits at a Critical Cable Crossroads
Cable routes linking Europe and Asia frequently pass through or near the Middle East, including chokepoints like the Red Sea and the Suez region, making the area strategically vital to global east-west internet connectivity.
The United Arab Emirates and other Gulf states host significant landing stations, positioning the region as a genuine hub rather than merely a pass-through corridor.
A Handful of Cables Carry a Disproportionate Share of Traffic
Because certain routes, such as those crossing the Atlantic between the United States and Europe, carry especially heavy volumes of data, a relatively small number of high-capacity cables handle a disproportionately large share of total global bandwidth.
This concentration is one reason telecom analysts pay close attention to capacity additions on these specific busiest corridors rather than treating all new cable systems as equally significant.
Governments Treat Cable Infrastructure as Critical National Security
Given how much economic and communications activity depends on undersea cables, many governments classify this infrastructure as critical to national security, monitoring landing stations and coordinating with allied nations on protection measures.
Deliberate sabotage of cables, while historically rare, has drawn increased official attention in recent years as a recognized geopolitical risk alongside the far more common accidental damage from fishing and shipping.
Cable Capacity Keeps Scaling Faster Than Most People Realize
Advances in optical technology have repeatedly multiplied how much data a single fiber pair can carry, meaning newer cable systems carry vastly more capacity than cables laid just a decade or two earlier along similar routes.
This scaling is part of why global internet capacity has kept pace with soaring demand from video streaming and cloud services without requiring an equally dramatic increase in the number of physical cables.
Old Cables Are Eventually Retired, Not Left Running Forever
A submarine cable system typically has a designed operational lifespan of around 25 years, after which degrading components, outdated technology, or simple economics make continued operation impractical compared to newer alternatives.
Retired cables are sometimes left in place on the seafloor rather than removed, since retrieval is often more costly and environmentally disruptive than leaving the inert cable undisturbed.
Undersea Cables Also Carry Scientific Sensors Today
Some newer cable projects integrate scientific sensors directly into the cable structure, capable of detecting seismic activity, ocean temperature, and pressure changes, turning existing internet infrastructure into a tool for earthquake and tsunami monitoring.
This dual-use approach lets researchers gather ocean floor data across vast stretches of previously unmonitored seabed without funding an entirely separate sensor network.
Redundancy, Not a Single Perfect Cable, Keeps the Internet Resilient
No single cable is considered too critical to fail. Instead, global internet resilience depends on redundancy, multiple cables along different routes so that traffic can automatically reroute if one system is damaged or goes offline.
Regions with fewer redundant cable connections experience far more noticeable internet disruptions from a single break than regions served by many overlapping systems.
Building a Major Cable System Takes Years and Billions of Dollars
Planning, permitting, manufacturing, and laying a major transoceanic cable system typically takes several years from initial announcement to activation, with costs for the largest systems running into the hundreds of millions or even billions of dollars.
Regulatory approval alone, involving multiple countries' governments along the route, can take as long as the physical construction and installation work itself.
Some Countries Remain Reliant on Just a Few Cable Connections
Certain island nations and countries with limited coastline access still rely on a comparatively small number of cable connections to the rest of the world, leaving them more exposed to outages than countries with dense, overlapping cable networks.
International development organizations and telecom investors have specifically targeted improving cable redundancy for such vulnerable countries in recent years.
Deep-Sea Cable Repair Ships Operate Around the Clock, Globally
A relatively small international fleet of specialized cable repair ships is positioned around the world, ready to be dispatched to any break location, since even a brief delay in repair can cause significant economic disruption for the affected region.
These ships use remotely operated underwater vehicles to locate and retrieve damaged cable sections from the seafloor before splicing and resealing them for redeployment.
Insurance and Legal Frameworks Govern Cables in International Waters
Once a cable passes beyond a country's territorial waters into international waters, it is governed by international maritime law rather than any single nation's regulations, with specific conventions addressing cable protection, liability for damage, and repair rights.
Cable operators also carry substantial insurance against damage and outages, since a major system represents a significant financial investment exposed to real physical risk over its operational life.
Data Centers Cluster Near Major Cable Landing Points
Because latency and bandwidth costs rise the farther data must travel over land after coming ashore, cloud providers and internet companies often build major data centers close to cable landing stations to minimize the added distance.
This clustering effect helps explain why certain coastal cities have become outsized global hubs for cloud infrastructure, disproportionate to their population or economic size alone.
New Routes Are Being Planned to Avoid Overloaded Corridors
As traffic through the busiest existing corridors, such as those crossing the Red Sea, approaches capacity or faces heightened geopolitical risk, telecom operators actively plan alternative routes across other seas and land bridges to diversify global connectivity.
This ongoing diversification effort is a direct response to the concentration risk created when too much of the world's connectivity depends on a small number of overlapping chokepoints.
What Most People Get Wrong About How Their Internet Reaches Them
It is a common misconception that a streaming video or an overseas video call travels mostly through space via satellites. In reality, almost the entire journey happens along physical fiber-optic cables, most of it lying quietly on the ocean floor.
Satellites do play a growing role for remote connectivity, but they remain a supplement to, not a replacement for, the undersea cable network that carries the vast majority of the world's international data.
Sources
- TeleGeography: Do Submarine Cables Account for Over 99% of Intercontinental Data Traffic? β industry data explainer
- Submarine Cable Map: 2Africa β route, length, and connected countries
- Meta Engineering: 2Africa Pearls subsea cable β official project details
- Wikipedia: Transatlantic telegraph cable β 1858 and 1866 history, cross-checked against historical accounts
FAQ
What percentage of internet traffic actually goes through undersea cables?
Roughly 99 percent of intercontinental internet traffic travels through undersea fiber-optic cables. Satellites carry less than 1 percent of this traffic, playing a supporting rather than central role.
When was the first undersea cable ever laid?
The first attempted transatlantic telegraph cable was laid in 1858, connecting Ireland and Newfoundland, though it failed after only a few weeks. A durable, lasting transatlantic cable was completed in 1866.
What is the longest undersea cable in the world?
The 2Africa cable, backed by Meta and telecom partners, is roughly 45,000 kilometers long, making it the longest submarine cable system ever built, connecting 33 countries across Africa, Europe, and Asia.
What usually damages undersea cables?
Most damage comes from human activity in shallow coastal waters, particularly fishing trawlers dragging equipment along the seafloor and ships dropping anchors, far more often than from sharks or other marine wildlife.
How thick is a typical undersea internet cable?
In deep ocean sections, a cable is often no thicker than a garden hose. Near the coast, in shallower, higher-risk waters, cables are wrapped in extra armor and become considerably thicker.
Who owns the undersea cables the internet relies on?
Ownership includes telecom carriers, national operators, and increasingly major technology companies like Meta, Google, Amazon, and Microsoft, which now directly fund and co-own significant cable systems.
How long does it take to repair a broken undersea cable?
Repairs typically take anywhere from a few days to a couple of weeks, depending on weather, water depth, and the availability of a specialized repair ship near the break location.
How many undersea cable systems are active worldwide today?
There are several hundred active submarine cable systems worldwide, collectively spanning well over a million kilometers of cable and connecting nearly every populated coastline.
Where can you see a real map of the world's undersea cables?
TeleGeography maintains the Submarine Cable Map, a public, regularly updated interactive map showing active and planned cable systems, their landing points, and ownership worldwide.
Why do repeaters need to be placed along undersea cables?
Light signals weaken over long distances through fiber. Repeaters, spaced roughly every 60 to 80 kilometers, amplify the optical signal so data remains readable across thousands of kilometers.
How long does an undersea cable typically last before retirement?
A submarine cable system is typically designed to operate for around 25 years before degrading components and outdated technology make it more practical to retire than to keep maintaining.
Can a single cable cut take down a whole country's internet?
Yes, for countries with limited redundancy. Nations relying on only one or two cable connections can lose most of their international internet capacity until a break is repaired, which is why redundant connections matter.
Do undersea cables serve any purpose beyond carrying internet data?
Yes. Some newer cables integrate scientific sensors that detect seismic activity, ocean temperature, and pressure changes, effectively doubling as tools for earthquake and tsunami monitoring.
Why does the Middle East matter so much for global cable routes?
Cable routes linking Europe and Asia frequently pass through Middle East chokepoints like the Red Sea and Suez region, and Gulf states host major landing stations, making the area a genuine connectivity hub.
Roughly how much does it cost to build a major undersea cable system?
The largest transoceanic cable systems can cost hundreds of millions to billions of dollars, and take several years from planning and permitting through to activation.
About the Author
We reference Wikipedia and other authoritative sources to explain the background and current understanding of this topic.
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