In 2012, a survey by the Chesapeake Bay Program found the Bay had 48,191 acres of submerged aquatic vegetation (SAV), or underwater grasses,down from the 72,935 acres estimated by data gathered in 2004. This is just 26 percent of the 185,000-acre goal for the Bay and its tidal tributaries, down from 39 percent in 2004. Extreme weather conditions in recent years have contributed to the decrease.