Oceans and lakes are no longer sites for limitless exploitation. Climate change, pollution, unregulated harvesting, aquaculture, and invasive species are all involved in stories that heighten a sense of crisis, and frame marine resources as entities in need of protection. Within this climate of governance, there is an intensified search for knowledge. Marine and freshwater species are interpreted, counted, surveilled, classified and inscribed in various forms This panel addresses how we know and engage with fish and other marine species. We explore human-fish ontologies. We ask about fish sentience, and how a sense of the other is mediated across the water surface. We notice that fish are objects and agents as well as symbols and signs, and welcome ethnographies that link stories of the past with ways we re-present the future. We invite the multi-sited, multi-logic and multiple ways in which human-fish relations are assembled, disassembled, practised, governed, politicised and possibly policed.