Sailors huddle to account for their classmates as they complete the final dunk and lap swim exercise during a simulated storm at the Aviation Survival Training Center at Naval Air Station Whidbey Island. Students at ASTC go through a series of evolutions including a simulated helicopter crash, parachute drags and survival techniques after exiting downed aircraft. This two-day refresher course is mandatory every four years for anyone who flies in U.S. Navy and Marine Corps aircraft.