The Canadian Maritimes are heavily reliant on groundwater, with PEI 100% dependent on its sandstone aquifer for water supply. Groundwater resources on PEI have faced recent compounding stresses due to increasing demand, nitrate contamination from agriculture, and changing meteorological and oceanic conditions. Freshened Offshore Aquifers (FOAs) may represent a new freshwater resource for PEI, and for similar settings worldwide. SOURCE is an exploratory study of fresh submarine groundwater resources offshore of PEI in the Gulf of St. Lawrence. We hypothesize that ice sheet and landscape dynamics contributed to recharge of FOAs hosted in fractured consolidated clastic sediments. Accordingly, a 9-week research expedition onboard the RV Maria S Merian was conducted in fall 2021. Data from geophysical surveys using multichannel seismic reflection profiles and controlled-source EM, along with multibeam bathymetric data and sediment gravity cores, were collected to explore FOAs. Preliminary results highlight the existence of FOAs but require more analysis and interpretation, including hydrogeological modeling. Coastal hydrogeological investigations on PEI are being conducted concurrently with the offshore SOURCE project to elucidate onshore-offshore aquifer connections and dynamics. An island-wide groundwater elevation map and numerical groundwater model have been developed to study regional groundwater dynamics, water budget, and seaward groundwater flow. Coastal drone-based thermal surveys have been conducted at low tide to map springs for monitoring to provide insight into submarine groundwater discharge patterns and quality. Understanding onshore and offshore groundwater dynamics and their connections will help ground the implementation of recent PEI water legislation in hydrogeologic science.