This paper examines struggles between an NGO and state water authorities over the causes and consequences of Lake Sasyk’s polluted water and over whether to undertake a restoration project. In the late 1970s, a Soviet agro-industrial project tried to turn the salt-water Sasyk estuary (in Odessa Oblast) into a freshwater lake to irrigate fields. The project, which constructed a 14 km dike and a canal transporting fresh water from the Danube River, had disastrous consequences. Since the mid-1990s, activists from a local NGO have campaigned for an official decision to de-dike Sasyk. This paper considers two issues in disputes over the future of this failed irrigation project: first, the political struggles between the NGO and canal management authorities to produce, refute, and conceal knowledge about Sasyk’s complex water environments; second, how the strategy of this movement is shifting from one that acknowledged the importance of science in determining the condition of water in Lake Sasyk to one that challenges scientists’ ontological and epistemological assumptions about what water is, and how one can know its condition and effects on human life.