The coastal aquifer of Ras Jebel is located in the northeastern governorate of Bizerte. It is formed by a Mio–Plio-quaternary geological structure. The region of Ras Jebal is considered an important agricultural centre due to intensive groundwater exploitation. This overexploitation results in a decrease in piezometry and an increase in salinity. The groundwater piezometric study shows a decrease in the piezometric level of approximately −3.34 to −1.79 m in 2015. Our study based on vertical electrical sounding had the aim to monitor the salinity of the water table in 2017, which showed that refill transactions in the aquifer of Ras Jebel caused the improvement of the chemical quality of water. In fact, the salinity in the coastal zone is between 2.53 and 4.14 g/L. As for the resistivity, which reached 2 Ω m near the sea, the geophysical study based on the geoelectric method has provided an electrical image of the basement to clarify the basin structure. The use of an electrical prospection method to study the salinization of the water table of Ras Jebel has highlighted the contribution to the most origin of saltwater: natural origin (sea water intrusion) on the northeastern coast of Ras Jebel. This source is the main origin of the degradation of the quality of underground water resources in Ras Jebel.