U.S. Navy Hospital Corpsman 2nd Class Dylan Rich, right, a preventive medicine technician with Navy Environmental and Preventive Medicine Unit 6, helps Hospital Corpsman 1st Class Andre Cooper, center, check air and ventilation quality during an industrial hygiene class aboard the hospital ship USNS Mercy (T-AH 19) July 24, 2014, in the Pacific Ocean as part of Rim of the Pacific (RIMPAC) 2014. RIMPAC is a U.S. Pacific Fleet-hosted biennial multinational maritime exercise designed to foster and sustain international cooperation on the security of the world's oceans. (U.S. Navy photo by Mass Communication Specialist 3rd Class Justin W. Galvin/Released)