120718-N-WA347-081 PACIFIC OCEAN (July 18, 2012) The guided-missile cruiser USS Princeton (CG 59) and the aircraft carrier USS Nimitz (CVN 68) are underway in formation during the Great Green Fleet demonstration portion of the Rim of the Pacific (RIMPAC) 2012 exercise. Princeton and Nimitz took on a 50-50 blend of advanced biofuel and traditional petroleum-based fuel. Twenty-two nations, more than 40 ships and submarines, more than 200 aircraft and 25,000 personnel are participating in the RIMPAC exercise from June 29 to Aug. 3, in and around the Hawaiian Islands. The world's largest international maritime exercise, RIMPAC provides a unique training opportunity that helps participants foster and sustain the cooperative relationships that are critical to ensuring the safety of sea lanes and security on the world's oceans. RIMPAC 2012 is the 23rd exercise in the series that began in 1971. (U.S. Navy photo by Mass Communication Specialist 2nd Class Eva-Marie Ramsaran/Released)