ABSTRACT The fluid qualities of water include its propensity to yield, to dissolve, and to accommodate intrusive structures and projects. The possibilities for aquacultural expansion appear limitless, yet the presence of aquaculture excludes and transforms other life-forms. While terrestrial expansions mark their presence through infrastructure such as fences and walls, aquatic infrastructures are more elusive. This article takes the current capitalist scenarios of aquacultural expansion as a starting point for reflecting on the scalability of plantation economies in coastal waters. Assessing the possibilities and limitations of ocean-as-infrastructure for aquatic frontiers, it explores water as a means of production, a medium, and an externality, and asks: How might more than economic forms of fluid dispossession follow in the wake of marine extractive industries? Engaging the notion of ocean frontiers and aquatic commons, the article draws on ethnographic research on Norwegian salmon aquaculture and Sámi river entanglements.