The floodplain of the Himalayas is a land formed and destroyed incessantly by the water of its rivers. Measures intended for flood control, aimed at separating productive land from river water through earth levees, have instead worsened the inundations, disrupting the beneficial flow of soil through floodwaters, obstructing water drainage, and resulting in enormous waterlogged areas. This article proposes that the failure of flood control in Bihar, India, is due to misunderstanding the river as a matter of water only, hence attempting the conceptual naturalization of an otherwise relative ontological distinction between water and land. Local knowledge of water reveals that neither water nor land can even be named, let alone understood, without the other. Informed by ethnographic fieldwork and multidisciplinary research in North Bihar, this article presents land and water as being in intimate correspondence with each other. By virtue of comparison, the ethnographic encounter is held to defy other ontologies of water that see the two substances as being in opposition. As a result, this article posits ontologies of natural substances as ‘watertight’, sclerotic, mutually exclusive, unable to adapt, and prone to be caught in a semiotic conflict.