Water space should be considered a common good that belongs to nobody and everybody. Yet policymakers and real estate developers are currently driving the transformation of Hamburg’s industrial waterfronts along the Bille River. Confronted with the threat of gentrification and displacement, local stakeholders are demanding that the Bille River be seen as a common good, accessible as both social infrastructure and neighborhood open space. By codesigning the production of a Walk-In Map and an Expandable Archive with local NGO HALLO: e.V., we developed a tool to communicate the existing practices of neighborhood use, appropriation, and maintenance along the banks of the Bille River. This work makes it possible to integrate local uses, potentials, and needs into future planning processes.