The participating Municipalities, sharing a bond of geographical, physical and tourist similarities, have identified in the underwater world and in their respective natural resources, the starting point for the development of this project, which unwinds around the theme of the sea and its underwater natural and archaeological resources. The common objective consists in the enhancement and promotion of the marine environment through the creation of a cross-border network of underwater routes characterised by various degrees of difficulty, available to beginners and expert scuba divers alike. Therefore joint underwater routes are devised, while information and reception centres are set up to concentrate the offer and ensure a rational management of the visits, encouraging a sustainable and organised tourism. The actions were carried out jointly by the three partner Municipalities. The first phase consists in a research of bibliographic data and the study of diving points of a naturalistic and/or historic/archaeological interest, located off the coasts of Caorle, Grado and Koper - Capodistria. There follows the construction of underwater routes proper (four in each Municipality) which are precisely mapped, illustrated through photos and videos and catalogued. All resulting material will then be exhibited in the didactic-tourist facilities set up in the three towns. Lastly, the project entails the preparation of a set of detailed maps of the twelve diving areas, providing detailed information to engage in scuba diving in full safety. Each map contains the outline of the route and the most significant points of interest, as well as technical information and detailed descriptions, as well as curious facts and in-depth highlights.