10 Intriguing Insights into the Submarine Cables Powering the Internet

Neal Stephenson famously likened Earth to a computer motherboard when describing the intricate web of wires that make up the internet. From cables strung between telephone poles to warnings about buried fiber optics, we’re constantly reminded that the internet is essentially a vast network of lengthy wires. However, what we see above ground is just the tip of the iceberg. The majority of this infrastructure lies hidden in the frigid depths of the ocean. Here are 10 lesser-known facts about the undersea cables that keep the world connected.

1. Laying cables is a slow and costly process.

Over 95 percent of global data travels through submarine communication cables resting on the ocean floor. These cables stretch hundreds of thousands of miles and can reach depths of 8000 meters—comparable to the height of Mount Everest. Specialized ships, known as cable-layers, handle the installation. It’s not as simple as dropping weighted wires; the cables must be carefully laid across flat seabed areas, avoiding coral reefs, sunken ships, fish habitats, and other ecological or physical obstacles.

Shallow water cables are roughly the diameter of a soda can, whereas deep water cables are slimmer, about the width of a Magic Marker. This difference stems from the reduced risk of damage in deeper waters, where there’s less activity. Shallow cables are buried using high-pressure water jets to protect them. Regardless of the route, installing these cables is a monumental task, often costing hundreds of millions of dollars per project.

2. Sharks have attempted to snack on the internet.

Experts are divided on why sharks occasionally bite submarine communication cables. Some suggest it’s due to electromagnetic fields, while others believe it’s curiosity or even a prelude to a land invasion. Regardless of the reason, sharks have been caught damaging these cables, though “fish bites” make up less than 1 percent of all cable faults, according to the International Cable Protection Committee. To combat this, companies like Google have started using shark-resistant coatings to protect their cables.

3. The internet faces as many risks underwater as it does on land.

Every few years, a construction worker accidentally severs a cable, cutting off internet access for an entire region. While the ocean lacks bulldozers, it presents its own dangers. Beyond sharks, undersea cables are threatened by boat anchors, fishing activities, and natural disasters. A Toronto company has even proposed laying a cable through the Arctic to link Tokyo and London. Once deemed impossible, this idea is now feasible due to melting ice, though it remains extremely costly.

4. The concept of global connectivity via undersea cables isn’t new.

The first transatlantic telegraph cable, linking Newfoundland and Ireland, began installation in 1854. By 1858, the first message was transmitted, stating: “Laws, Whitehouse received five minutes signal. Coil signals too weak to relay. Try drive slow and regular. I have put intermediate pulley. Reply by coils.” While not particularly inspiring, this marked a historic moment. (“Whitehouse” refers to Wildman Whitehouse, the Atlantic Telegraph Company’s chief electrician.)

For historical perspective: During the four years of cable construction, Charles Dickens was still penning novels, Walt Whitman released Leaves of Grass, the town of Dallas was officially established in Texas, and Abraham Lincoln, then a Senate candidate, delivered his famous “House Divided” speech.

5. Underwater cables are a favorite target for spies.

At the peak of the Cold War, the USSR frequently sent poorly encrypted messages between its key naval bases. Soviet leaders believed strong encryption was unnecessary, as the bases were connected by an undersea cable within their heavily monitored territorial waters. They assumed the U.S. would never dare to tap the cable, fearing it could spark World War III.

However, they underestimated the U.S.S. Halibut, a specially equipped submarine designed to evade Soviet detection. The sub located the cable, installed a massive wiretap, and returned monthly to collect recorded transmissions. This mission, known as IVY BELLS, was eventually exposed by Ronald Pelton, a former NSA analyst who sold details to the Soviets. Today, tapping undersea cables is a common practice among intelligence agencies.

6. Governments are now using submarine cables to evade surveillance.

The U.S. holds a significant edge in electronic surveillance due to its pivotal role in developing global telecommunications infrastructure. Major data routes often pass through U.S. borders and waters, simplifying wiretapping efforts. When Edward Snowden leaked documents revealing the extent of American data interception, many nations were furious. In response, countries like Brazil initiated projects like a submarine cable to Portugal, deliberately bypassing the U.S. and excluding American companies from participation.

7. Undersea cables are faster and more cost-effective than satellites.

With over 5000 satellites orbiting Earth in 2022, humanity has achieved remarkable feats like landing probes on comets, deflecting asteroids, and planning Mars missions. It might seem logical that space would be the ideal medium for the internet, rather than century-old undersea cables. However, this assumption is flawed.

Despite being developed in the same era, satellites suffer from latency and data loss, while fiber optic cables can transmit data at 99.7 percent the speed of light. For a glimpse of a satellite-dependent internet, visit Antarctica, the only continent without undersea cables. Bandwidth there is limited, hindering critical climate research, as stations generate more data than they can transmit via satellites [PDF].

8. Destroying the internet would require diving gear and a pair of wire cutters.

While cutting a submarine cable is challenging due to the thousands of lethal volts coursing through them, it’s not impossible. In 2013, near Alexandria, Egypt, divers in wetsuits deliberately severed the South-East-Asia-Middle-East-West-Europe 4 cable, a 12,500-mile link connecting three continents. This act slashed Egypt’s internet speeds by 60 percent until repairs were completed.

9. Repairing undersea cables is no simple task, but after 150 years, we’ve developed effective techniques.

Replacing a damaged submarine cable is far more complex than untangling an ethernet cord behind your desk. Specialized repair ships are sent to fix broken cables. In shallow waters, robots retrieve the cable and bring it to the surface. For deeper waters (over 6500 feet), ships use custom-designed grapnels to lift the cable. Sometimes, grapnels cut the damaged cable into two sections, allowing repair ships to mend each end separately above water.

10. The undersea internet infrastructure is designed to endure for 25 years.

By 2023, over 500 communication cables lay on the ocean floor. These submarine cables are built to last 25 years, remaining economically viable within that timeframe. However, global data usage has skyrocketed. In 2013, average internet traffic was 5 gigabytes per person. By 2023, Finland leads the world with nearly 36 gigabytes per month per broadband subscription. Thanks to advancements like phase modulation and submarine line terminal equipment (SLTE), existing cables have seen capacity increases of up to 8000 percent, ensuring they can handle today’s data demands.