An interdisciplinary group of geochemists, hydrologists,and biologists recently convened a conference to discuss mechanisms and impacts of advective exchange through permeable sediment systems at the terrestrial-marine interface. The format of the conference included 2 days of invited talks followed by working group sessions that focused on three critical areas of research: physical processes, diagenetic processes/organic carbon cycling, and process tracers. The overall theme of the conference reflected the growing recognition of the importance of sub-seabed exchange of coastal waters on the global mass balance of associated chemical species. Subterranean chemical exchange in coastal systems reflects a group of poorly constrained biogeochemical processes coupled with advective water exchange. This exchange occurs where ground waters or pore waters, ranging from saline to fresh, are cycled through permeable solids as a consequence of pressure gradients.