Contemporary coastal cities intertwine variegated stakes, linked to the economic, productive and social functions of the seashore, and need a correct management aimed at balancing the different needs and at maintaining a high ecological status of the coasts themselves. A fracture emerges between the urban development of coastal areas and the social desire and expectations of the 'urban coastal society', a community intimately connected to the coast and sea elements. Port and productive evolution has often neglected the socio-recreational component inherent in coastal areas, related to its attractiveness for citizens, the presence of natural qualities and an undeniable visual and perceptual value that influence the use of these places, influencing the conformation of coastal public spaces. The integrity of the urban coasts appears fragmented by the juxtaposition of variegated elements which can however be considered as pieces of a potential green-blue infrastructure, with a view to recomposing the city-sea interface. The contribution aims to investigate the management and design criticalities that affect urban blue spaces, mainly in relation to the implications related to leisure and sociality, proposing a historical, spatial and socio-perceptive comparison between Naples and Marseille.