Mapping undersea cable risk from bathymetry to geopolitics: Evidence-based rankings and tailored resilience strategies

Undersea communication cables carry more than 95 percent of the world’s data traffic, yet their security remains poorly understood. Recent sabotage incidents in the Baltic, Red Sea and Taiwan Strait highlight an urgent need for policy-relevant risk assessments, particularly in the Indo-Pacific where strategic rivalry, dense traffic and complex seabed topography intersect. This article quantifies and explains cable-security risk across three contrasted cable systems—Unity/EAC Pacific (Japan–U.S.), Asia-America Gateway (Guam–Hawaii), and Tata TGN-Tata Indicom (India–Singapore)—to derive targeted resilience measures. We combine an expert survey and semi-structured interviews to assess risk across landing sites, maritime zones, and cable systems, and employ the Friedman test (with Kendall’s W effect sizes) to evaluate whether expert ratings differ systematically across maritime zones and tension levels in a repeated-measures design. The results show patterned heterogeneity rather than uniform vulnerability. Experts broadly agree that landing stations are attractive targets, but risk is location specific. Cable-system differences are also evident with Indian Ocean systems judged less vulnerable than Pacific systems, owing to redundancy and greater costs associated with sabotage. Bathymetry, surveillance, and proximity to adversaries often outweighed other variables with experts also highlighting gray zone phases as prime sabotage windows. Building on these findings, we propose a six-point policy framework for actors to adopt tiered, scenario-based security postures; prioritize protection at the segment/system level; strengthen early-warning for gray zone risks; conduct operationally focused vulnerability assessments; develop regional seas frameworks to pool assets; and ensure national readiness through audits, single points of contact, and codified public–private protocols.