PACIFIC OCEAN (July 18, 2012) Secretary of the Navy (SECNAV) the Honorable Ray Mabus and Rear Adm. Tim Barrett, commander of the Australian Fleet, shake hands after signing an energy efficiency pact during the Great Green Fleet demonstration portion of the Rim of the Pacific (RIMPAC) 2012 exerciseexercise aboard the aircraft carrier USS Nimitz (CVN 68). Nimitz took on 200,000 gallons of biofuel for the demonstration. Twenty-two nations, more than 40 ships and submarines, more than 200 aircraft and 25,000 personnel are participating in 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 3rd Class Renee Candelario/Released) 120718-N-XA289-035 Join the conversation www.facebook.com/USNavy www.twitter.com/USNavy