The Verge has a really good – though very long – article on the maintenance of the cables that keep the world connected to the internet: The Cloud Under the Sea. These cables are laid under the seas and oceans, sometimes thousands of meters deep, and this is exactly as vulnerable as it sounds… even though they carry 95% of all of the world’s data.
The world’s emails, TikToks, classified memos, bank transfers, satellite surveillance, and FaceTime calls travel on cables that are about as thin as a garden hose. There are about 800,000 miles of these skinny tubes crisscrossing the Earth’s oceans, representing nearly 600 different systems […]. The cables are buried near shore, but for the vast majority of their length, they just sit amid the gray ooze and alien creatures of the ocean floor, the hair-thin strands of glass at their center glowing with lasers encoding the world’s data.
If enough cables get damaged, entire regions get disconnected, essentially cut off from the world; and yet, most people are unaware that the Internet even functions via underwater cables, let alone the 22 ships and their crew whose entire life revolves around fixing them.
If, hypothetically, all these cables were to simultaneously break, modern civilization would cease to function. The financial system would immediately freeze. Currency trading would stop; stock exchanges would close. Banks and governments would be unable to move funds between countries because the Swift and US interbank systems both rely on submarine cables to settle over $10 trillion in transactions each day. In large swaths of the world, people would discover their credit cards no longer worked and ATMs would dispense no cash.
…
Contemplating the prospect of a mass cable cut to the UK, then-MP Rishi Sunak concluded, “Short of nuclear or biological warfare, it is difficult to think of a threat that could be more justifiably described as existential.”
Fortunately, there is enough redundancy in the world’s cables to make it nearly impossible for a well-connected country to be cut off, but cable breaks do happen. On average, they happen every other day, about 200 times a year. The reason websites continue to load, bank transfers go through, and civilization persists is because of the thousand or so people living aboard 20-some ships stationed around the world, who race to fix each cable as soon as it breaks.
Nonetheless, sometimes during bigger catastrophes, enough cables get damaged that regions do go dark:
On [2006] December 26th, an earthquake dislodged sediment on Taiwan’s southern coast and sent it rushing 160 miles into the Luzon Strait, one of several global cable chokepoints. Nine cables were severed and Taiwan was knocked almost entirely offline. Banking, airlines, and communications were disrupted throughout the region. Trading of the Korean won was halted. The cables, buried under mountains of debris, were nearly impossible to find. It took 11 ships, including the Ocean Link, nearly two months to finish repairs.
The work of these maintenance ships is difficult, and sometimes they have to work insane schedules, such as during the 2011 March 11 earthquake in Japan and the subsequent tsunami:
The earthquake had caused more than 20 faults, and the Ocean Link had repaired 11 of them. It had taken 154 days of continuous work. They had missed a time of national mourning, school graduations, harvest celebrations, and the slow resumption of normalcy.
Imagine a job that requires you to work 154 days consecutively, without much of a break, let alone a holiday. Together with how unknown this entire industry is, such working conditions certainly do not make it easy for them to continue finding the people they need.