This essay looks at early‐modern Venice hydroculture as a case of episteme from below. The forms of water knowledge it developed were multilayered and collective in their essence and solidly rested on a social experiential basis that was rooted in labour (especially fishing) and practices (especially water surveying and engineering). In accordance with the city's republican esprit (and correspondent political values), its episteme emerged as the encounter and negotiation between various institutions and groups: the fishermen of San Niccolò in Venice, (...) the practitioners of the water magistrature and political authorities. This essay explores the institutional settings of this water culture, seen as an instance of bottom‐up epistemic construction. It especially addresses three historical instances: firstly, a seventeenth century program to map public waters in order to block their alienation for private fish farming; secondly, water officers’ interviews with fishermen aimed to assess the state of the lagoon hydromorphology and, thirdly, fishing regulations. Venice communitarian and circular forms of knowledge production are here contrasted to an opposite paradigm, which was embodied by the Galileian mathematician and Rome courtier, Benedetto Castelli. His interactions with the Republic of Venice on water management and his approach to hydraulic problems are revealing of an elitist and abstract understanding of scientific knowledge that guided political decisions from above without taking in any consideration the opinions of the ‘vulgar’. While his science was the expression of a top‐down political epistemology, Venetian water knowledge was more egalitarian. It left room for exchange, inclusiveness and bottom‐up codification; it valued the gathering of different experiences (including the fishermen's practical knowledge of their waters) and rested on a concrete and systemic (organicist) understanding of natural‐anthropic processes. (shrink)