The U.S. Geological Survey (USGS), in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and the Massachusetts Office of Coastal Zone Management (MA CZM), is producing detailed geologic maps of the coastal sea floor. Imagery, originally collected by NOAA for charting purposes, provides a fundamental framework for research and management activities along this part of the Massachusetts coastline, shows the composition and terrain of the seabed, and provides information on sediment transport and benthic habitat. Interpretive data layers were derived from multibeam echo-sounder and sidescan-sonar data collected in the vicinity of Edgartown Harbor, Massachusetts. During August 2008 seismic-reflection profiles (Boomer and Chirp) were acquired, and during September 2008 bottom photographs and surficial sediment data were acquired as part of two ground-truth reconnaissance surveys.