From the scientific and literary expression ‘flux et reflux’ to the political and juridical language of the ‘citoyens du navire,’ the ocean as a physical and social space is a salient thread over time and across genres in Montesquieu's political thought. Amidst the high tides of maritime expansion and oceanic trade, Montesquieu's perspective of the sea, far from static, evolved along with the thinker. This essay for the first time uses the space of the sea to navigate Montesquieu's rhetorical choices, historical perspectives, and temporal-spatial concerns, by tracing maritime themes in Montesquieu's oeuvres both chronologically and thematically. It points out that Montesquieu's early-expressed interest in the sea tides, which arose in the oceanographic context in a Résomption (1720), morphed into political metaphors in the Lettres Persanes (1721), the Pensées and L’esprit des Lois (1748). And through his study of the actual seas during his journey in Italy, recorded in the Voyages, Montesquieu further advanced his thought on the sea as a significant site of social and political activity. The goal is to bring to the fore an underlying strain of thought that preoccupied Montesquieu's intellectual development, which may in turn better contextualise his political thought in its formation.