This text examines the Mediterranean as a contested space constituted through multiple lines of tension, rather than as a unified entity. Drawing on diverse disciplinary traditions – from Braudel's historical-cultural analysis to the Black Mediterranean intersectional approach – the issue conceives the Mediterranean as a “boundary object”: sufficiently stable to maintain identity, yet malleable enough to assume new meanings across different social worlds. While acknowledging how EU border policies – memoranda with Libya and Tunisia, SAR zones redefinitions, hotspots – materially reinforce barriers through the racialisation of maritime space, the special issue also highlights how the same context generates encounters and solidarity practices. The articles collected analyse three interconnected dimensions: the material aspects of border assemblages and their role in producing the migrant as “alien” subject; the complex interplay between necropolitical measures and practices of solidarity; and methodological innovations developed through “seawork” – an ethnographic practice engaging with the sea, favouring collective writing and circular analysis, thus unsettling epistemologies inherited from land-based research.