There are 1.5 million kilometres of submarine communications cables on the ocean floor, organized into 607 systems. They carry effectively all intercontinental internet traffic. If they fail at scale, satellites cannot replace them. That is the baseline reality from which every resilience question flows. The vulnerability profile is dominated by human activity, not geology. Eighty-six percent of cable faults trace to fishing gear or ship anchors, with fishing roughly twice as prevalent. Geological events account for 7%, abrasion 4%, and component failure just 4%. Nearly half of all faults occur in territorial waters, and almost all the rest in exclusive economic zones. Only 2% happen on the high seas. The deep ocean is the safest place for a cable; the danger is at the edges, in shallow water where ships operate and cables must come ashore. Geographic chokepoints concentrate this risk to an alarming degree. The Bab al-Mandab Strait channels 16 cables between Asia, Europe, and the Middle East — several were severed in September 2025, disrupting an estimated 25% of regional capacity. The Singapore Strait hosts 35 cable systems in shallow, heavily trafficked water. The Luzon Strait between Taiwan and the Philippines carries 18 cables and was the site of the 2006 earthquake that severed all of them, requiring 11 repair vessels and 49 days to restore service. The Matsu Islands case illustrates how sustained disruption works in practice. The two submarine cables connecting the archipelago to Taiwan's main island were cut 27 times between 2018 and 2022, with four major outages from 2023 to 2025. The Baltic Sea has seen 11 disruptions to submarine systems since 2023. Whether these patterns reflect bad luck, grey-zone warfare, or both, the effect is the same: repeated isolation of connected communities. Defenses are layered but fundamentally limited. Cables in deep water are just 20mm polyethylene-wrapped fibre — the size of a garden hose — with no external armour. Steel jacketing is added only near shore. Cable Protection Zones warn vessels away from cable routes, but enforcement in contested waters like the Bab al-Mandab or Black Sea is functionally impossible. Cable routing tries to minimize exposure to geological risk, hostile waters, and political complications, but chokepoints impose hard geographic constraints. The geopolitical dimension is sharpening. The article traces deliberate cable-cutting to 1914, when Britain severed Germany's transatlantic telegraph cables on the fourth day of World War I, forcing Germany onto wireless communications that British intelligence could intercept. The same tactic was repeated in 1939. Modern cable routing must now account for FCC restrictions on landing in adversary territories, Houthi-controlled waters that are ungovernable for cable protection, and Russian-contested zones in the Black Sea where routine maintenance is impossible. The structural problem is clear: the global internet depends on physical infrastructure that is thin, unarmoured in its most extensive segments, concentrated through a handful of narrow straits, and protected primarily by legal zones that assume good-faith compliance. Around 200 faults occur worldwide per year, a number that has stayed steady even as cable inventory grows. The system works because redundancy absorbs individual failures. But the chokepoints — Bab al-Mandab, Singapore, Luzon — represent correlated failure risks where redundancy collapses, because all the backup cables run through the same strait.
