__Abstract__ In this paper, we explore how managing actors' boundary judgments influence the adaptability of water governance. We approach this question by examining the relationship between the way water managers frame, and act in, complex water issues on the one hand and develop adaptive water governance strategies on the other. We define four categories of boundary judgments made by water managers in order to deal with the complexities in water governance issues. An in-depth case study analysis of an attempt to adjust the management of the water regime in the south-west Delta of the Netherlands is provided in order to reconstruct the water managers' boundary judgments and their impact upon governance strategies used. We found that, most of the time, the water managers involved predominantly made tight boundary judgments. These tight boundary judgments seemed to hamper the mutual learning process among a variety of stakeholders that is needed to realize adaptive water governance. We argue that wide boundary judgments enhance the chance of realizing adaptive practices and build upon exploration, learning, and connection.