160322-N-TC720-006 CORFU, Greece (March 22, 2016) -Gunner's Mate Seaman Vincent Marez, from Denver, swaps out the barrel of a .50 caliber machine gun aboard USS Donald Cook (DDG 75) March 22, 2016. Donald Cook, an Arleigh Burke-class guided-missile destroyer, forward deployed to Rota, Spain is conducting a routine patrol in the U.S. 6th Fleet area of operations in support of U.S. national security interests in Europe. (U.S. Navy photo by Mass Communication Specialist 2nd Class Mat Murch/Released)