Navigation under water is a special challenge for divers and often a risk factor that should not be underestimated. A reliable system for positioning could mean an increase in safety, as well as support the practice of special forces in emergency organizations (fire department water service, military divers, water rescue, etc.). This is precisely the aim of the Scubanav exploratory project, which lays the foundations for the development of such a GNSS-based underwater navigation system. This involves the use of surface buoys equipped with a GNSS receiver, which determine their position and transmit GNSS-like underwater signals, which the underwater receivers use to determine their position. Scubanav is working on the technological requirements to evaluate the implementation of such an underwater navigation system. Through the participatory involvement of different user groups (recreational divers, firefighters, military divers, professional divers), the technology will be designed to meet the needs of the users.