The undersea domain has emerged as a critical arena of strategic competition where legal ambiguity, technological change, geopolitical rivalry, economic dependence, and environmental pressures converge to generate new forms of insecurity. Existing scholarship, however, largely examines these challenges in isolation, limiting understanding of how vulnerabilities interact. This paper argues that undersea insecurity is fundamentally a cross-domain governance problem and develops a five-dimensional analytical framework to explain how interacting legal, technological, geopolitical, economic, and environmental vulnerabilities shape small-state security. Drawing on elite interviews conducted between 2025 and 2026 with naval officers, policymakers, maritime experts, and academics in Sri Lanka and Singapore, the paper compares how two small maritime states experience, interpret, and respond to similar undersea challenges. The analysis demonstrates that vulnerabilities are not produced by individual risks but by cascading interactions across multiple domains, while governance outcomes are shaped by institutional capacity, technological capability, and strategic culture. Although both states confront comparable structural pressures, Sri Lanka’s fragmented governance and limited capabilities amplify vulnerability, whereas Singapore’s integrated governance, technological investment, and institutional coordination interrupt cascading risks. The paper advances maritime security scholarship by reframing undersea security as an interactive, multidimensional governance challenge and offers a framework for analysing small-state agency in an increasingly contested underwater environment.
Keywords: Undersea security; underwater governance; small states; maritime security; cross-domain vulnerabilities
