Sailors aboard USS Donald Cook (DDG 75) draw out the nixie system as part of an anti-submarine warfare drill. Donald Cook, an Arleigh Burke-class guided-missile destroyer, homeported in Rota, Spain, is conducting naval operations 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 Karolina A. Oseguera/Released)