Submarine groundwater discharge (SGD) is an important process responsible for transporting terrestrial dissolved chemical substances into the coastal ocean, thereby impacting the marine ecosystem. Despites its significance, there are few studies addressing SGD in the northern Baltic Sea. Here we investigate the potential occurrence of SGD in an area characterized by seafloor terraces formed in varved glacial clay located around Fif & aring;ng Island, Southern Stockholm Archipelago. We analyzed Rn-222 activity and porewater geochemistry in both marine and terrestrial sediment cores retrieved from Fif & aring;ng Island and its surrounding offshore areas. Results from 222Rn mass-balance calculations, water isotopes, salinity, chloride concentration, and dating (including 14C and helium-tritium dating) indicate that modern groundwater flows through varved glacial clay layers and fractured rocks on Fif & aring;ng Island and discharges into Fif & aring;ng Bay. Additionally, the offshore cores reveal a saline groundwater source that, dating of the dissolved inorganic carbon, appears systematically younger than the hosting clay varves dated using the Swedish clay varve chronology. Acoustic blanking in our acquired subbottom profiles may be related to this fluid migration. The occurrence of this saline groundwater seems to be independent from the distance to the submarine terraces. Collectively, our study confirms the occurrence of submarine groundwater in the varved glacial clay close to Fif & aring;ng Island and further offshore. Our findings help establish the significance of submarine groundwater discharge in influencing the past and present coastal environment in the Baltic Sea region.