When you send an email, make a video call, or stream your favorite show, you probably don’t think about how that data reaches its destination. Most people assume the internet operates through satellites, but in reality, 99% of global internet traffic travels through undersea fiber optic cables. These massive cables, lying on the ocean floor, connect continents and make our hyper-connected world possible.
Yet, despite their critical role, undersea cables remain one of the least talked-about aspects of global infrastructure. What happens when a cable breaks? How secure are these deep-sea data highways? And how are they shaping the future of internet speed and security?
Let’s dive into the top 10 fascinating facts about undersea fiber cables, starting with some of the most surprising realities behind these technological marvels.
1️⃣ They Carry 99% of the World’s Internet Traffic 🌍
It’s a common misconception that satellites handle most international internet traffic. While satellites are crucial for remote areas and military applications, undersea fiber cables are the real workhorses of global connectivity.
📌 Why Undersea Cables Dominate:
- Faster Speeds: Fiber optic cables have much lower latency than satellites, meaning data moves almost at the speed of light with minimal delay.
- Higher Capacity: A single fiber-optic cable can carry hundreds of terabits per second (Tbps), far exceeding satellite capabilities.
- More Reliability: Satellite internet can be affected by weather conditions, whereas fiber cables are much more stable.
📌 The Numbers:
- There are more than 550 undersea cables spanning over 1.3 million kilometers (800,000 miles)—enough to circle the Earth 32 times!
- The world’s longest undersea cable, SEA-ME-WE 6, stretches 19,200 km (12,000 miles), connecting Europe, Africa, and Asia.
🛠️ Underwater Fiber Insight:
Even Elon Musk’s Starlink satellites rely on fiber optics to transmit data between ground stations. In reality, fiber and satellite internet work together, rather than one replacing the other.
2️⃣ They Are as Thick as a Garden Hose—But Incredibly Tough 💪
Despite carrying nearly all of the world’s internet traffic, undersea fiber cables aren’t massive. They’re surprisingly thin, often no wider than a garden hose or soda can. But don’t be fooled by their size—these cables are built to withstand some of the ocean’s harshest conditions.
📌 What’s Inside an Undersea Cable?
- Glass Fibers: Transmit light signals carrying data at near-light speed.
- Steel Armor: Protects against external pressure and deep-sea hazards.
- Waterproof Coating: Prevents corrosion and water damage.
- Shock Absorption Layer: Shields against deep-sea earthquakes and ocean currents.
📌 Strength and Depth:
- Cables in deep ocean waters (up to 8,000 meters/26,000 feet deep) only need minimal protection because they are far from human interference.
- In shallow waters, they are heavily armored to withstand fishing activity, ship anchors, and accidental damage.
- Some cables are buried under the seabed to provide extra protection in high-risk areas.
🛠️ Underwater Fiber Insight:
Even though they are durable, cables still break about 100 times per year due to natural disasters, ship activity, and even shark bites! But thanks to redundancy (multiple cables serving the same regions), global internet traffic keeps flowing.
3️⃣ Sharks, Anchors, and Earthquakes Can Cut Internet Access 🦈⚓🌍
Undersea fiber optic cables are incredibly tough, but they aren’t invincible. Various factors can damage or completely sever these cables, disrupting internet access in entire countries.
📌 Biggest Threats to Undersea Cables:
- Ship Anchors & Fishing Nets (65% of Breakages)
- Many cables run through shallow waters near major ports. A single dropped anchor or trawling fishing net can snap a fiber-optic cable, causing widespread outages.
- In 2008, a severed cable in the Mediterranean knocked out internet access for 75 million people across the Middle East and South Asia.
- Earthquakes & Natural Disasters (20% of Breakages)
- Seabed shifts from earthquakes and underwater landslides can break multiple cables at once.
- The 2006 Taiwan earthquake cut six major undersea cables, disrupting financial markets and communications across China, Hong Kong, and Japan for days.
- Shark Attacks (Yes, Really!)
- Sharks are naturally attracted to electromagnetic fields, which can sometimes cause them to bite undersea cables.
- While rare, incidents have occurred where sharks have punctured the protective layers, leading to data loss.
📌 How Are Breakages Fixed?
- Specialized cable repair ships (only about 60 in the world) locate and retrieve the damaged section of cable.
- The cable is brought to the surface, spliced (repaired), and lowered back down—a process that can take several days to weeks.
- Backup cables and redundant routing ensure that most regions don’t lose connectivity entirely when one cable is damaged.
🛠️ Underwater Fiber Insight:
Countries with fewer cable connections are more vulnerable. In 2018, a single undersea cable failure knocked out internet access for the entire country of Mauritania for 48 hours!
4️⃣ Some Cables Are Owned by Tech Giants Like Google and Facebook 💰
While undersea fiber cables were traditionally built and operated by telecom companies and governments, tech giants like Google, Meta (Facebook), Amazon, and Microsoft are now investing heavily in their own private cable networks. Why? Because controlling internet infrastructure gives them a massive competitive advantage in speed, reliability, and cost savings.
📌 Big Tech’s Fiber Expansion:
- Google owns or co-owns over 20 undersea cables, including the Dunant cable, which connects the U.S. and France with 250 terabits per second (Tbps) capacity.
- Meta (Facebook) is building the world’s longest cable, “2Africa,” a 45,000 km (28,000 mi) long cable designed to improve internet access in Africa, Europe, and the Middle East.
- Amazon and Microsoft use dedicated cables to power their global cloud services (AWS & Azure).
📌 Why It Matters:
- Tech companies now have direct control over their own global data transfers, reducing reliance on traditional telecom providers.
- Private cables ensure faster speeds and lower latency for their services, improving cloud computing, video streaming, and online collaboration tools.
- Some of these companies are even offering excess bandwidth on their private cables to governments and smaller ISPs.
🛠️ Underwater Fiber Insight:
Big Tech isn’t just laying cables—they’re developing AI-powered monitoring systems to predict and prevent disruptions before they happen.
5️⃣ The Deepest Undersea Cable Lies 8,000 Meters (26,000 Feet) Below the Ocean 🌊
Laying fiber cables isn’t as simple as dropping a wire into the ocean. The seabed is a hostile, extreme environment, with cables needing to survive crushing pressure, freezing temperatures, and geological shifts. Some cables sit at depths where even submarines can’t reach them.
📌 Deepest Undersea Cables:
- The Mariana Trench, the deepest point on Earth at 10,994 meters (36,070 feet), has multiple fiber-optic cables running through it.
- The Japan-U.S. Cable Network, a critical trans-Pacific link, reaches depths of 8,000 meters (26,000 feet) in some locations.
- Repairing deep-sea cables is extremely difficult—cables deeper than 1,500 meters (5,000 feet) are usually left unburied because human activity (like fishing) isn’t a risk.
📌 How Are Cables Laid at These Depths?
- Specialized cable-laying ships use giant reels to deploy fiber across the ocean floor, mapping the safest routes.
- The process takes weeks or even months, depending on the route and ocean conditions.
- Underwater robots (ROVs) are sometimes used to inspect or repair cables in extreme depths.
🛠️ Underwater Fiber Insight:
Despite running thousands of miles across the ocean floor, undersea cables rarely go in straight lines. They are carefully mapped to avoid undersea mountains, trenches, and geological fault lines.
6️⃣ Governments Use Undersea Cables for Surveillance and Cybersecurity 🕵️♂️
Undersea cables don’t just carry internet traffic—they’re also prime targets for surveillance, espionage, and cyber warfare. Some governments monitor or tap undersea cables to intercept data, while others focus on securing them from foreign threats.
📌 Real-World Examples of Cable Surveillance:
- The NSA’s “Operation Tempora” (Revealed by Edward Snowden)
- The U.S. and U.K. have tapped into undersea cables to monitor global internet traffic for intelligence gathering.
- Russia’s Underwater Spy Submarines
- Russia operates special submarines, like the Losharik, designed to tamper with or tap into undersea cables.
- China’s Great Firewall Relies on Fiber Infrastructure
- China heavily monitors data flows through key undersea cables connecting to Hong Kong, limiting access to external internet services.
📌 How Countries Protect Undersea Cables:
- Cybersecurity Threat Monitoring: Governments and ISPs use AI-driven network monitoring to detect unauthorized access attempts.
- Military Protection: The U.S. Navy and NATO patrol areas near critical undersea cable junctions.
- Cable Redundancy: To prevent any one country from shutting down the internet, multiple cables are built along similar routes.
🛠️ Underwater Fiber Insight:
In 2013, Egypt arrested three divers trying to cut a critical fiber cable off the coast of Alexandria. The attack briefly slowed down internet speeds across the Middle East.
7️⃣ They’re So Valuable That Some Countries Are Fighting Over Them ⚔️
Undersea fiber cables aren’t just about internet access—they’re also multi-billion-dollar assets that connect the global economy. That’s why some countries compete, argue, and even threaten military action over cable routes and access points.
📌 Geopolitical Disputes Over Undersea Cables:
- China vs. U.S.
- The U.S. has blocked multiple China-linked undersea cable projects, fearing they could be used for espionage and data theft.
- The Pacific Light Cable Network (PLC) was supposed to connect Hong Kong to the U.S., but the U.S. forced Facebook & Google to reroute it.
- The Arctic Race
- Melting ice is opening new seabed routes for fiber cables, with Russia, the U.S., and Canada competing to control Arctic data corridors.
- EU vs. U.K. Over Brexit Impact on Cables
- After Brexit, the U.K. had to renegotiate data-sharing rules, since many of its fiber connections pass through EU waters.
📌 Why It Matters:
- Control of fiber cables = control of global data flow.
- Some governments could cut off rival nations by severing access to key cables.
- Countries like Australia and Japan are rapidly expanding their own cable networks to reduce dependence on U.S. and China-controlled cables.
🛠️ Underwater Fiber Insight:
Some experts fear that in a future cyberwar, countries may physically cut undersea cables to disrupt economies and communication.
8️⃣ They Can Now Detect Earthquakes and Tsunamis 🌊
New research has shown that undersea fiber cables can act as massive seismic sensors, helping detect earthquakes, undersea landslides, and even tsunamis before they strike land.
📌 How It Works:
- Light signals inside fiber cables are disrupted by seismic activity.
- AI-powered systems analyze these disruptions in real time to detect and locate earthquake epicenters.
- Scientists can track movements of tectonic plates across vast ocean regions using existing fiber networks.
📌 Real-World Examples:
- In 2021, researchers at Google used subsea cables to detect earthquakes near California and Chile.
- Japan and the Pacific Northwest are developing fiber-based tsunami warning systems, potentially giving coastal cities precious minutes to evacuate.
🛠️ Underwater Fiber Insight:
If fiber-based seismic tracking becomes mainstream, we could double or triple global earthquake detection capabilities—without building new infrastructure.
9️⃣ The Internet Could Go Dark Without Fiber Cable Upgrades 🚨
The world’s demand for data is exploding, but undersea fiber cables aren’t being upgraded fast enough to keep up. This has led to growing concerns that major regions could suffer bandwidth shortages within the next decade.
📌 The Problem:
- Internet traffic is doubling every 2-3 years, but new cable projects take 5+ years to complete.
- Many existing cables were built 20+ years ago, and some are nearing the end of their lifespan.
- Countries that depend on only one or two fiber cables (like Pacific island nations) risk total internet blackouts if an outage occurs.
📌 Solutions Being Developed:
- Next-gen fiber cables (800G and beyond) can carry up to 5x more data than older cables.
- AI-powered network optimization helps squeeze more performance out of existing cables.
- More backup cables are being built to prevent single points of failure.
🛠️ Underwater Fiber Insight:
By 2030, global data demand could outpace existing undersea cable capacity, forcing companies to either invest massively in upgrades or face slowdowns and outages.
🔟 Quantum Internet Could Make Fiber Cables Unhackable 🔐
The biggest cybersecurity threat to undersea cables isn’t physical damage—it’s data interception. Right now, with the right tools, governments and hackers can secretly tap fiber cables to steal or manipulate data. But quantum technology could change that forever.
📌 How Quantum Fiber Networks Work:
- Quantum encryption uses “qubits” that change state when observed—meaning hacked data becomes useless.
- China has already tested quantum-secured fiber connections between Beijing and Shanghai.
- Future undersea fiber cables may be completely immune to cyberattacks using quantum key distribution (QKD).
📌 Why It’s a Game-Changer:
- Governments and businesses will have completely secure global data transfer.
- Quantum-secured fiber could make hacking obsolete, forcing cybercriminals to find new methods.
- Financial transactions, military communications, and personal data will be safer than ever before.
🛠️ Underwater Fiber Insight:
Quantum-secured undersea cables are already in development, with the U.K., U.S., China, and the EU investing heavily in next-gen encryption for global data networks.
Undersea fiber cables are the lifelines of the internet, enabling everything from streaming Netflix to billion-dollar financial trades. But they are also fragile, geopolitically contested, and under increasing strain.
As the world’s data needs grow, we’ll need more advanced cables, better cybersecurity, and smarter ways to protect this hidden infrastructure. Whether through AI monitoring, seismic detection, or even quantum encryption, the future of undersea cables is more exciting—and more critical—than ever.
