Researchers at The Ohio State University and NASA's Jet Propulsion Laboratory have created the first-ever map of key regions of "submarine groundwater discharge," where freshwater and seawater mix unseen below ground. The previously hidden sites mark areas of vulnerability for ocean contamination and drinking water contamination. Areas in dark blue are vulnerable to pollution from land to sea. Areas in pink are vulnerable to pollution from sea to land in the form of saltwater intrusion. Areas in light blue are vulnerable to both.