Gridded multibeam bathymetry and sidescan-sonar imagery together cover approximately 21.6 square kilometers of sea floor in eastern Long Island Sound offshore of Rocky Point, New York. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11251, these acoustic data, and the sea-floor sampling and photography stations subsequently occupied to verify them, (1) show the composition and terrain of the seabed, (2) provide information on sediment transport and benthic habitat, and (3) are part of an expanding series of studies that provide a fundamental framework for research and resource management (for example, cables, pipelines, and dredging) activities in this major East Coast estuary.