Recently, the global Ocean has become a key (environmental) diplomatic issue. However, behind the apparent coherence of international events, the development of this “ocean diplomacy” remains a hesitant and fragmented process involving multiple actors and tensions, which this seminar co-organized by the ODIPE collective aims to examine. The three successive UNOCs (New York in 2017, Lisbon in 2022, Nice in June 2025) are sometimes presented by their promoters as conferences of the parties (COP). However, these conferences are not intended to negotiate a specific international treaty: they are open spaces for discussion, meetings, power struggles, and storytelling about the global Ocean. This process of a of diplomacy are marked by proliferation, uncertainty, and varied strategies. The scenes and meanings  are difficult to grasp in all their complexity, interconnections—even for the research communities most directly concerned. Collective ethnographies, in interaction with the entire ocean science community, facilitates understanding and reporting on what is at stake. The seminar will bring together these ethnographic field reports and the experiences of participants in these events to engage in a critical interdisciplinary dialogue.