The objective of this study was to assess the impacts of U.S. Navy-sponsored navigation channel modification and maintenance activities conducted from 1985-1992 on the shoreline in the vicinity of the traditionally called St. Marys Entrance. This inlet, separating Cumberland Island, Georgia, to the north and Amelia Island, Florida, to the south, contains a large estuary, a commercial and recreational port, Fernandina Harbor, Florida, and, since the 1970s, a U.S. Navy submarine base located at Kings Bay, Georgia. A study of the coastal area included the following components: (a) Review of historical data and previous studies. (b) Numerical simulation of waves and shoreline change. (c) Monitoring of waves water level, shoreline position, beach profile and sediments, and ebb-tidal bathymetry over the period 1988-1992. No adverse impact on the beaches of Cumberland Island and Amelia Island by U.S. Navy navigation channel modification and maintenance at St. Mary Entrance could be detected in any of the analyses or monitoring performed in this study. (AN).