This special issue combines insights from an array of theoretical perspectives, including political ecology, Indigenous studies, and more-than-human and feminist geographies to engage with a critical question for water studies: What are the theoretical, empirical and methodological implications of a closer engagement with the matter and properties of water and infrastructure? To answer this question, the contributions draw on a geographically and empirically diverse set of case studies that illuminate a range of articulations of materiality of water and infrastructures in hydro-social assemblages. Collectively, the papers highlight how the materiality of water is inherently plural, as it is co-constituted through its entanglement with other materialities (water with), gives rise to emergent materialities through its intra-action with other elements and more than human natures (more-than-water), and relies on the labour of living organisms to transform and maintain its function (lively waters). Second, the papers show how apprehending and pluralising materiality of water and infrastructure extends conceptualisations of agency, justice and care in hydro-social assemblages. The third thread emerging from this collection of papers is that methods matter for interdisciplinary, community and more-than-human knowledges. We conclude by identifying potential areas of interdisciplinary practice and future research on the material matters of water/s and infrastructures that engage with the interplay between ecological, hydrological, technical and social processes.