This book delves into the concept of city-sea interface as a space of strong physical, ecological, social and functional connection between the edge of the city and the edge of the water, recalling the idea of an urban amphibious, in relation to its flexibility to community, environmental and management issue that prevent the sustainable development of urban coasts. In particular, the volume relates the spatial planning of littoral spaces with the demands of contemporary urban coastal society, since such complex places constitute crucial hubs for the fruition of coastal ecosystem services. The work explores these topics in the Euro-Mediterranean context, with regard to densely urbanised land-water areas through a methodological framework. A legal analysis describes the main coastal governance and Maritime Spatial Planning guidelines and how they are incorporated in national littoral management systems; the geo-spatial approach defines a spatial data model for the socio-environmental features of the interface; finally, the psycho-social approach aims at studying the social representations in relation to accessibility, uses and planning adaptation. This framework is proposed as a benchmarking tool: specifically, it has been applied to Marseille and Naples, two similar Mediterranean cities with complex city-sea interfaces. Moreover, it may also support the implementation of coastal-maritime planning at a local scale.