The work delves into the international, European and national regulations on fresh and marine waters, in a systemic logic, aimed at surveying their public and private profiles according to an interdisciplinary method, taking into account the plural and multilevel dimension of the reference regulation. The rules of inland waters are treated, in particular those on the ownership of riverbeds and watercourses and maritime state property, as well as the codictic rules on private waters (in the context of the publicization of all waters introduced in Italy since 1994) are examined in depth. In addition, sea management rules are analyzed, specifically highlighting the responsibilities of companies in the pollution of marine habitats, and the provisions of the environmental code on wastewater discharges are explored in depth. Finally, water is examined as a resource, in the context of planning, programming and protection (including at the global level) of water assets.