At first encounter, “water” and “cognition” seem like a paradoxical pairing. Water is fluid, running where it will; in Heraclitus's famous formulation, we cannot step into the same river twice. In contrast, “cognition” may seem hard and spiky, analytic, fixed. But as this collection shows, the two terms are not in opposition to each other. First, cognition is not simply “in the head”; like water, thinking spreads and seeps and leaks into the world. To label a process “cognitive” is not to relegate it to brainbound ratiocination; instead, our authors imagine “thinking” in rich and dynamic coordination with emotions, with the built and natural environment, and with the social world. Cognition is thus embodied, emotional, and deeply embedded in its cultural and material environments, which change across history and context. Cognition is acting: remembering, imagining, dreaming, gesturing, making, moving, grieving, forgetting, narrating. These “doing” verbs also remind us that thinking is always multiple, embedded and extended—that is, ecological.

And because “cognition” is always on the move, distributed across minds, bodies, artifacts, and other people, it is necessarily historical, shaped with and by the tools, environments, and socialities humans encounter, transform, and are subjected to. Since the concept of cognitive ecology is predicated upon the porous boundaries among mind, body, and world, a force as powerful and multi-variant as water is particularly well suited to this approach.