This article explores the relevance of water in the cultural traditions of indigenous Lumad peoples of Mindanao island in the southern Philippines. Historically, Lumad identities and networks (whether political, social, or economic) were conceptualised according to the rivers on which people dwelt. Important ties stretched from the coast to the interior (i.e., between upriver and downriver communities), with water providing the path of least resistance in rough terrain. This stands in contrast to the present-day cultural and political divide between the uplands and lowlands, which are now dominated by mainstream ‘Filipino’ settlers, referred to locally as dumagat or ‘sea-people’. Given that Lumad ties to the land are profoundly visualised according to rivers, the salt-water origins of dumagats locate these interlopers at, or more often, beyond the moral boundaries of the Lumad universe. Meanwhile, in Lumad oral traditions, the movements of people across one generation to the next are traced according to river systems they have occupied, with proximity to water often equated with degree of civilization and cultural purity. Despite the passage of time, and decreased linear proximity from the original rivers, these primal riverine origins remain significant in the present day, as Lumads continue to socially prioritise the genealogies and networks of traditional political authority that are upstreamed from these oral traditions. Focusing on field data from the Higaunon ethnic group of northern Mindanao, this article analyses five examples of water being employed as a hermeneutic for how Lumads locate themselves in relation to other ethnic groups, the state, modern Filipino society, and their own cultural traditions.