For more than a thousand years, the building of seawalls has been the dominant strategy to cope with flood risk in the coastal wetlands of the North Sea area. In debates on coastal adaptation, the seawall has become a symbol of "hard" infrastructure contrasting with "soft" engineering and "building-with-nature" technologies. Inspired by both environmental history and STS, this article challenges dominant narratives on the history of seawalls as inevitably evolving towards the rigid infrastructures we know today. Throughout history, seawalls responded to changing and varying socio-spatial realities. Pronounced differences were not so much situated in technical evolutions or external environmental pressures, but rather in the changing organization of labor (and capital), the power and knowledge claims embedded in the seawall and their interaction with the physical environment. Despite improvement-rhetoric, "modern" seawalls were not inherently "superior" or "more effective" than their more localized predecessors. They just corresponded to different realities.