Water management is crucial to lead sustainable development of our societies, and to be effective needs for a detailed characterization of the water resources availability, through the knowledge of their reservoir’s main properties in terms of geometries and physical properties. In this way it is mandatory to plan responsible exploitation and use protocols, increasing the system resilience. Usable groundwater scarcity is in fact a major issue to be overcome with smart territorial management. In view of this, the knowledge derived from direct and indirect diagnostic investigations is a key factor to balance the societal pressure over such delicate targets. In the early Twenty-thousands, a geophysical survey using High-Resolution (HR) reflection seismic and time domain electromagnetics (TDEM) was carried out in the south-eastern part of the island of Sardinia, Italy. The main objective of the survey has been to study a very complex coastal aquifer situated in an area where a – still present – huge saltwater intrusion phenomenon had already occurred mainly due to anthropic overexploitation linked to tourism and agriculture. Within this paper, the TDEM results, constrained by seismics, are presented and discussed.