The article argues that British maritime museums do more to represent the nation than the sea, thereby contributing to nation-building discourse, and offers an alternative way of thinking about belonging through the lens of maritime mobilities. The United Kingdom’s national maritime museums are, of course, but a few among many museums seeking to incorporate a more diverse range of community voices and perspectives into their collections and exhibitions. Yet maritime museums are a particularly pertinent example of Britain’s nation-building discourse due to the global reach of Britain’s seaborne colonialism and exploration, and the concomitant range of their galleries. The article discusses the National Maritime Museum in Falmouth, Cornwall (NMMC) in the wider context of how maritime museums depict the nation. It argues that the NMMC’s presentation of the sea illustrates how nation-building connects with colonialism in latent, largely unacknowledged ways that are broadly representative of Britain’s maritime museums. The article concludes that were maritime museums to take seaborne mobility as a starting point for decolonialised exhibits, they would provide visitors with a greater range of tools with which to critically analyse Britain’s maritime histories, the legacies of which are still being played out today.