VIRGINIA BEACH, Va. -- Laurie Sorabella, with Oyster Reef Keepers of Virginia, places a bag of 1,000 spat, or baby oysters, in a tub of Lynnhaven River water Oct. 15, 2011. Sorabella teaches oyster gardening classes to Hampton Roads teachers, so they in turn can create oyster gardens with their students. The oysters in the tub demonstrated how oysters clean the water -- an adult-sized oyster can filter up to 50 gallons of water a day.