Every time you send a message, stream a show, or make a video call to someone on the other side of the world, you might imagine the data is traveling through satellites high above the Earth. In reality, the majority of global internet traffic moves through a vast network of undersea cables, laid across the ocean floor. These cables, some as thin as a garden hose, carry more than 99% of all international data, connecting 57 countries and serving over 4.5 billion people. The network spans 1.48 million kilometers, with more than 694 separate systems, forming the backbone of the global digital economy. Without these submerged cables, the internet would essentially stop working. The importance of these cables has grown significantly over the years. The first transatlantic fiber optic cable was installed in 1988, linking the United States and Europe. Since then, the landscape has changed dramatically. Major tech companies like Google, Meta, Microsoft, and Amazon now not only use these cables but also invest heavily in their construction and maintenance. These companies have recognized the strategic value of undersea cables, treating them as critical assets comparable to their data centers. In France, this trend is visible in Marseille, which now hosts 17 undersea cables—up from 13 in 2020—placing it among the world’s top five connectivity hubs. Despite their importance, undersea cables face a variety of threats. While shark bites—drawn to the electromagnetic signals of the cables—are a well-documented but relatively rare issue, more common dangers include ship anchors, fishing nets, and trawling activities, which can sever a cable in seconds. Additionally, geopolitical tensions have made these cables a point of concern. In recent years, there have been suspicions of intentional sabotage or espionage targeting undersea infrastructure, raising questions about digital sovereignty and national security. These concerns were addressed at an international summit in Porto, Portugal, last winter, where experts focused on improving the resilience of these vital systems. A single cut to an undersea cable can have far-reaching effects. It can disrupt internet access for entire regions, slow down emergency services, and even paralyze economic activities. Such disruptions are not just hypothetical—there have been several documented cases where undersea cable cuts caused significant outages. This fragility has driven a continuous effort to build and replace cables, as older systems, with an average lifespan of about 25 years, are reaching the end of their useful life. At the same time, the demand for internet bandwidth continues to grow. These efforts, though largely invisible to the public, are essential to maintaining the seamless digital world we rely on daily.