More than 600 submarine fiber-optic cables resting on the ocean floor carry roughly 99 percent of global internet traffic and 10 trillion dollars in daily financial transactions. Protected by armor near coastlines and garden-hose widths in the deep sea, these lines face frequent damage from ship anchors and fishing gear.
The modern digital economy relies less on fluffy cloud infrastructure and far more on a vast, vulnerable network of physical lines spanning the globe. According to reporting, more than 600 submarine cables on the seafloor, over 1.5 million kilometers of fiber-optic lines carry nearly every email, financial transaction, and stock trade on Earth. Satellites handle well under one percent of that digital traffic. These physical lines are vital not just for browsing websites and watching videos, but also for supporting critical sectors that include financial services, cloud computing, telecommunications, and government agencies.
Engineering the Seafloor: How Submarine Cables Survive the Depths
Laying communication lines across ocean basins requires complex engineering. Submarine fiber-optic cables extend over 1.5 million kilometers—connecting countries and continents. These lines are not simply dropped blindly onto the seabed, but instead undergo engineering designs aimed at protecting them from surrounding conditions. They feature multiple layers of external protection to help resist pressure, impacts, and various ocean-floor factors. Engineers plan routes carefully before laying the cables to stay as far as possible away from seismic activity zones, shipping lanes, and known fishing areas. In shallow areas and close to coasts, cables can be buried beneath the seafloor to provide an extra layer of protection, particularly where vessel traffic or fishing activities increase.
In the deep ocean, each line is roughly the width of a garden hose, housing individual fibers as thin as a human hair that manage massive loads of data, carrying your bank transactions and everyday communications.
The Real Threats: Ship Anchors Versus Marine Myths
Despite heavy external layers designed to resist pressure and impact, submarine infrastructure faces continuous disruption, and these lines do not entirely avoid breaking. Roughly 100 to 150—or about 200 total according to broader fault tracking—cables suffer breaks annually, requiring specialized repair operations. Human activity drives the vast majority of these faults. Boat anchors and fishing gear cause roughly two-thirds of all line failures, reaching the ocean floor and causing complete cuts or severe damage.
Public imagination often blames sharks for severed lines, and while shark attacks are not purely fiction and can cause damage, these incidents make up a very small fraction of total damage at roughly 1 percent. Confirmed fish-bite faults totaled exactly zero between 2007 and 2014. Instead, heavy commercial shipping gear poses the greatest risk. In late 2024, a cargo ship’s anchor dragged the seabed over 100 miles, cutting two Baltic cables. Geopolitical tensions have also heightened security concerns, turning the safety of submarine cables into an increasingly important security issue. Since 2023, approximately 12 cables have suffered cuts in the Baltic Sea amid suspicions that some incidents resulted from intentional acts of espionage, sabotage, or deliberate destruction targeting telecommunications infrastructure.
Maintenance Fleets and Satellite Limitations
When a line fails, repair ships must drag up the severed ends and splice them back together by hand on the open water before lowering the cable back down. The entire planet relies on a dedicated fleet of roughly 60 cable ships globally, with less than 20 dedicated specifically to repairs.
While satellite constellations provide essential backups—such as keeping Ukraine online when the wires got bombed—a lifeline is not a main line and they cannot match submarine capacity. More than 10,000 Starlink satellites are up in orbit representing over half of all satellites ever launched, but every satellite from every company adds up to about 50 terabits per second, whereas undersea cables carry around 8,750 terabits per second, with one modern cable beating the entire Starlink fleet combined. Even satellite signals ultimately rely on ground stations plugged into the same terrestrial fiber network, with space handling just the final few miles while the ocean handles the heavy lifting.
