The NEPTUNE EVOLUTION project (PatrimoNio natUralE sommerso e gesTione sosTeNibiLe della subacquEa ricreativa — EVOLUTION — IF Marittimo00198) aims to enhance and monitor underwater natural capital, as well as to promote the environmental sustainability of recreational diving in the cross-border area between Italy and France. This project is a follow-up to NEPTUNE, ended in 2022, which involved the assessment of the natural capital associated with each diving site in the Portofino Marine Protected Area (MPA). The assessment was carried out following a protocol developed within the national EAMPA project (Environmental Accounting in Italian Marine Protected Areas), for the ecological assessment of natural capital in Italian MPAs, including Portofino MPA. The protocol is based on the emergy analysis, a donor-side approach that quantifies, in biophysical terms, the resources the environment has invested in to generate and maintain stocks of natural capital. This work included: 1) the update of biomass used to assess natural capital of selected habitats; 2) the revision of coordinates and habitat distribution within diving sites; 3) the update of fish assemblages, associated with each habitat using visual census data collected in 2023 and assessed as number of individuals and biomass. The initial step involved the analysis of marine coastal habitat maps to estimate the surface area of each habitat of the MPA and within a 100-meter buffer around each diving site. Two primary results have been obtained: 1) a new assessment of the entire Portofino MPA natural capital value and the simulation of different management scenarios; 2) the update of natural capital at diving sites using more recent and detailed data. These results provide scientific support for improving management of the Portofino MPA, contributing to the conservation of underwater natural capital while promoting the sustainable development of recreational diving.