Coastal aquifers are transitional zones that play a vital role not only providing water resources for coastal societies, but also controlling the exchange of water and chemical constituents between land and ocean and thus influencing coastal marine ecosystems. Traditionally, they have been approached by two different scientific communities, one which focuses on the sustainability of water resources and is particularly interested in sea water intrusion (SWI), and another which focuses on fluxes of solutes supplied by groundwater to the coastal ocean, i.e. submarine groundwater discharge (SGD). As a result, the understanding of the bidirectional groundwater-seawater fluxes is often partial and/or limited. Nevertheless, recent technological, methodological and knowledge advances (e.g. new (hydro)geophysics and (micro)biological approaches, improved (bio)geochemical analytical capabilities, development of new sensors and modelling tools) have allowed scientists to approach these coastal systems in comprehensive and integrative manner as never before. This session aims to bring together multiple disciplines and perspectives on coastal aquifer. We solicit studies involving SWI, SGD, or both, in order to advance a broad conceptual framework of groundwater in the land-ocean continuum and quantify the dynamic biogeochemical processes that occur across local to regional scales. A better understanding of SWI and SGD from hydrogeologic and oceanographic perspective can help improve management of coastal groundwater and ecosystems and assess its current and future global importance.