Reply An official said it was probably a thresher shark, and not a great white. Thresher sharks stun their prey with their tail. They are common in the region. (Rhode Island Department of Environmental Management) CHARLESTOWN, RI — East Beach in Charlestown was temporarily shot down Saturday after a lifeguard spotted a shark fin. The Department of Environmental Management told WJAR a shark was seen swimming about 10 to 15 yards offshore and then again 30 to 40 yards offshore. Rhode Island's Marine Fisheries Division said it was probably a thresher shark, and not a great white. Thresher sharks stun their prey with their tail. They are common in the region.