U.S. Air Force airmen assigned to Seymour Johnson Air Force Base prepare for the swimming portion of a Physical Ability and Stamina Test (PAST) in Goldsboro, N.C., Aug. 12, 2013. The PAST is required for airmen looking to transition into a special tactics career field, to include: pararescue, combat controller, special operations weather technician, tactical air control party and survivial, evasion, resistance and escape specialist. (U.S. Air Force photo by Airman 1st Class Brittain Crolley/Released)