Sustainable water management aims at balancing ecological and social needs to ensure the maintenance of ecosystem functions over generations. Accelerated climate, environmental and societal change and its dynamics challenge the resilience of complex socio-ecological systems and require constant adaptation. In this paper, it is argued that understanding ‘why’—rather than ‘how’—people adapt to environmental change and, thus, acknowledging the heterogeneity of actors leads to a broader range of adaptation dissemination strategies. Two case studies in Tanzania and Germany with different foci in human–water interaction and socio-political backgrounds are compared. Using a (semi)participatory qualitative system analysis approach helps identifying the heterogeneity of actors and their specific ways of reasoning. Hereby, the perceived interplay of uncertainty, emerging from environmental and socio-economic context, is further shaping how actors can play out their specific agency and how this influences their personal room of action and ability to adapt. The comparison shows that acknowledging this heterogeneity is important across regions and water management issues to develop a broader range of tailor-made adaptation strategies targeting at the environmental issue itself or at empowering and enabling the actors to foster sustainable and resilient water management.