Abstract: The Sino-Indian rivalry features an increasingly prominent maritime dimension amidst the countries’ naval buildups and deployments in the Indian Ocean Region (IOR) and Western Pacific. This study finds that the patterns of naval buildup and nature of the seas as an ambiguous, international medium do not necessarily shape mutual perceptions between China and India as pure security seekers. India’s concerns about China’s IOR forays revolve around its expanding bluewater naval capabilities, especially submarines, and port access. Beijing is wary of New Delhi’s reach into the Western Pacific and role within a perceived US-led containment scheme that allows it to leverage on partners’ bluewater assets. While war remains a remote prospect, this Sino-Indian rivalry at sea – extending from unresolved terrestrial political problems – looks set to persist.