This paper discusses five geophysical prospecting studies in coastal zones of the Iberian Peninsula in which the form and position of saline intrusion has, with great efficiency, been successfully determined. Geoelectrical prospecting is conclusively shown to be the most appropriate geophysical technique for this type of study, and in particular, electrical tomography, due to its speed, non-destructive nature and low cost. Electrical tomographs obtained in this way allow the position of saline intrusion in subsurface formations to be analysed, and optimising any future exploratory drilling in relation to its foreseen objective.