The first two papers of this panel explored the fluid and expansive geographies of belonging, extraction and circulation that permeated seemingly marginal Indian Ocean costal societies and moulded them into dynamic interfaces between Asia’s local worlds and the rest of the globe. This third paper takes a more macro-level perspective to sketch out how late 20th century Indian Ocean rim states, most of whom had recently emerged from colonial rule, sought to assert their legal, political and extractive sovereignty over their maritime borderlands. This included extending and enacting maritime boundaries as well as attempts to obtain and perform exclusive extractive control over the ocean’s fisheries and seabed resources, along with political campaigns for a zone of peace in the Indian Ocean. While such initiatives relied heavily on Afro-Asian ideas and networks, they were predicated on the erasure of the very oceanic space that stood at their geographic center. The imaginary promoted by the late 20th c. nation-state largely denied the Indian Ocean’s historical role as a meeting ground and a connective tissue, emphasizing its nature as a space for extraction and interstate relations instead. Yet these efforts rubbed against competing imaginaries and practices as well as against the ocean itself, underscoring the difficulty of bordering the sea.