The U.S. Geological Survey (USGS), in cooperation with the Connecticut Department of Environmental Protection and National Oceanic and Atmospheric Administration (NOAA), 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 Long Island Sound, shows the composition and terrain of the seabed, and provides information on sediment transport and benthic habitat. Interpretive data layers were derived from the multibeam echo-sounder data and sidescan-sonar data collected north of Plum Island, New York. During November 2009, bottom photographs and surficial sediment data were acquired as part of a ground-truth reconnaissance survey. For more information on the ground-truth survey see https://cmgds.marine.usgs.gov/fan_info.php?fa=2009-059-FA.