For many coastal nations in the Western Indian Ocean, and notably the islands of Madagascar, Mauritius, and Seychelles, the tuna fishery is considered one of the main pillars of economic development, providing jobs and substantial revenues while ensuring food security. However, the fishery is also an illustration of the paradox behind the idea of the blue economy, where economic growth and sustainable use of resources are promoted as jointly achievable. We show that a sustainability narrative, in which the idea of fishing within ecological limits is present within government policy, public discourse, and practices, is, however, in contradiction with the realities of accumulation and growth that prevail in the fishery. When measures towards ecological preservation are to be taken, geopolitics of access to the sea and tuna enter the stage and change the position and narrative of the same actors, governments, and industrial actors that promote sustainability. We emphasize the difficult and nearly impossible path of practicing sustainability in the current model of growth-driven tuna fisheries. We argue for the need to repoliticize the practice of sustainability through the questioning of what we see in tuna fisheries: a hegemonic narrative of sustainability and implicit growth, without positive socio-ecological transformations.