The application of the psycho-social approach to the city-sea interface of Marseille and Naples is hereby illustrated: specifically, the sociological survey focused on four similar urban areas in the two cities, namely productive and port areas, residential green areas, dense urban areas and urban beaches. The objective is to analyse how the various members of the urban coastal society enjoy the urban sea and coastline in relation to different characteristics of the city. Therefore, social perceptions, possible scenarios and awareness of the ecological and environmental dynamics underlying the sustainable development of the urban amphibious have been investigated.