This paper discusses ideas of anarchist (historical) geographies of rivers and seas. It does so by addressing works of early anarchist geographer Lev Ilich Mechnikov (mentioned here with the more known French spelling Léon Metchnikoff) (1838-1888), which lie at the origin of broader ‘Mediterranean metaphors’ comparing the globalising role of oceanic navigation to early Mediterranean connectedness, mainly discussed by Metchnikoff in his key book La civilisation et les grands fleuves historiques [Civilisation and Great Historical Rivers]. A close collaborator of Elisée Reclus and Peter Kropotkin and a multifarious scholarly talent, Metchnikoff provided contributions that still need to be fully rediscovered. Based on a systematic reading of Metchnikoff’s archives and works, I argue that, starting from historical rivers and the early Mediterranean, his ideas on the historical roles that can be possibly (and relationally) played by water-land assemblages can nourish current notions of more-than-wet ontologies and critical geopolitics. Eventually, these ideas provide models for understanding spatialities that are alternative to those of state borders, bounded land and terracentric territorialities, contributing to shape the open and boundless world that is currently conceived by scholarship informed to pluriversal notions of critical Mediterraneanism.