High resolution multibeam surveys to collect topographic and backscatter data at 300kHz were conducted in August 2001 and January 2005 on a set of artificial reefs along the south shore of Long Island, NY. The January 2005 cruise also included bottom photographs and groundtruthing of sediment characteristics with grab samples. The surveys of the reefs along the south shore demonstrated lateral variability in the surface sediment characteristics. Rates of morphological change can be determined where there were multiple surveys. In addition, a dramatic change in the texture of the bottom, which corresponds to biogenic structures is clearly visible in a large portion of the Fire Island Reef survey area. The presence of these biogenic structures in the geomorphology highlights the need to look at mesoscale temporal and spatial variability of the seabed and the role of the seabed as benthic habitats at more than one time in the year. This is particularly true in areas of proposed ‘industrial’ activity, so that important decisions are not made on insufficient data. Artificial reefs are particularly interesting because the surveys document variability in the seabed around very large anthropogenic structures on the seafloor, some of which are similar in scale to the proposed windmills. The mobility of sediment and the movement of bedforms can also be seen. The obviously active dynamics of the seafloor suggest that one needs to understand how active the seafloor is when placing such structures, and trying to assess their impact on the environment.