Studies of groundwater flow in coastal aquifers often focus strongly on freshwater and investigate flow in a narrow (<5 km) zone surrounding the coastline. This work was designed to place coastal flow in a regional context and to compare fresh and saline submarine groundwater discharge (SGD) for regional flow systems. Numerical flow and transport models were developed to estimate SGD associated with topography-driven flow, seawater recirculation, and geothermal convection in a passive margin setting. Simulations were based on two cross sections of North Carolina, and sensitivity studies were used to explore the impact of varying hydraulic and transport parameters. Results suggest that saline flow associated with seawater recirculation and geothermal convection should be considered in studies of SGD. Studies limited to shallow topography-driven flow may be justified in using small study areas, but flow systems contributing to SGD may span at least 20 km surrounding the coast and continental slope.