This paper examines notions and practices of participation in the management of one of Egypt’s limited but critical resources: water. Since the early 1990s, a number of international donors have promoted a shift towards participatory water management through the establishment of water user associations (WUAs). Based on the assumption that it is in the interests of those who use the majority of the water to manage it efficiently, these farmer organizations are designed to improve the system of water distribution. Drawing on a year of ethnographic fieldwork with a Dutch funded project, which is working through the Ministry of Water Resources to establish a WUA on every irrigation canal in Fayoum governorate, this paper explores the dynamics of participation in practice. Paying close attention to the fluidity of the resource in question, the paper asks how the material nature of the resource matters to the process of forming a participatory management community around it. The first section of the paper examines four understandings of participation that are variously held by irrigation engineers, farmers, policy makers, and international donors: participation as communication; participation as action; participation as economy; and participation as democracy. I argue that the divergence in perspectives about what the WUAs will actually do is critical to how this attempt to organize participation plays out. The second part of the paper looks at the process of constructing a community of water users. I contrast the forms of communal interaction that emerge in the fields through the farmers’ shared work of directing the flow of water with the project’s attempt to manufacture community around clusters of branch canals by organizing a series of meetings and elections. I argue that water’s fluidity, namely the difficulty of bounding water into a clear space of community-based management, lies at the root of the WUAs’ failure to attain widespread support and fulfill the role that their architects had in mind. Bringing an ethnographic lens to this examination of participatory resource management, the paper demonstrates the significance of the environment as a focal point of international intervention, community formation, and social mobilization in Egypt.