The intensifying extraction, privatization, and conservation of maritime spaces are transforming seascapes globally. Amidst rapid coastal change and the ambiguous reconfiguration of oceans as frontiers are coastal dwellers who occupy the shadows of these seascapes. In contrast to the capture of high-profile marine species, the harvest of the edible nests of balinsasayaw (swiftlet, Aerodramus fuciphagus) remains largely concealed at the interstitial spaces between land, coast, and sea. In the Philippines, harvesters known as busyador negotiate social relations, political networks, and karst systems to extract these lucrative nests. Despite the nest industry growing in value in Southeast Asia, we show how the busyador struggle in precarious social relations and spaces peripheral to coastal governance in northern Palawan Island. Building on the concept of ‘seascape assemblages’, we emphasize the importance of the less visible human-nonhuman relations that shape the nest harvest and trade. We trace the marginal social histories of the balinsasayaw by highlighting the precarious nature of the harvest, revealing how the busyador are subject to unfair working conditions, dispossession, and violence. We argue that as state actors and local elites reconfigure oceans as frontiers for development and conservation, struggles over labour and tenure rights, livelihood opportunities, and justice at sea are disregarded.