The Pacific region of Colombia, like many sparsely populated places in developing countries, has been imagined as empty in social terms, and yet full in terms of natural resources and biodiversity. These imaginaries have enabled the creation of frontiers of land and sea control, where the state as well as private and illegal actors have historically dispossessed Afro‐descendant and indigenous peoples. This paper contributes to the understanding of territorialisation in the oceans, where political and legal framings of the sea as an open‐access public good have neglected the existence of marine social processes. It shows how Afro‐descendant communities and non‐state actors are required to use the language of resources, rather than socio‐cultural attachment, to negotiate state marine territorialisation processes. Drawing on a case study on the Pacific coast of Colombia, we demonstrate that Afro‐descendant communities hold local aquatic epistemologies, in which knowledge and the production of space are entangled in fluid and volumetric spatio‐temporal dynamics. However, despite the social importance of aquatic environments, they were excluded from Afro‐descendants’ collective territorial rights in the 1990s. Driven by their local aquatic epistemologies, coastal communities are reclaiming authority over the seascape through the creation of a marine protected area. We argue that they have transformed relations of authority at sea to ensure local access and control, using state institutional instruments to subvert and challenge the legal framing of the sea as an open access public good. As such, this marine protected area represents a place of resistance that ironically subjects coastal communities to disciplinary technologies of conservation.