A U.S. Air Force pararescue trainee participates in a swimming exercise at Calaveras Lake in San Antonio, Texas, Aug. 17, 2011. Trainees must complete a rigorous nine-week physical conditioning and indoctrination program at Lackland Air Force Base, Joint Base San Antonio to become pararescuemen, who make up the only Department of Defense specialty specifically trained and equipped to conduct conventional or unconventional rescue and recovery operations.