Excessive input of nutrients to estuaries and the coastal ocean is a cause of eutrophication problems in many areas of the world. Direct discharge of groundwater has been identified as a key source of nitrogen into coastal waters in many areas, especially in the mid-Atlantic region. Monitoring and modeling of submarine groundwater discharge present many challenges for scientists who are attempting to describe and quantify physical, chemical, and biological processes, and communication of complex results to resource managers and infrastructure decision makers can be difficult. Successful projects often have led to development of novel and innovative methods and theories, as well as controversial management tools to reduce contaminant loads from groundwater to coastal ecosystems.