Ships and submarines participating in Rim of the Pacific exercise 2012 sail in formation in the waters around the Hawaiian islands. Twenty-two nations, more than 40 ships and submarines, more than 200 aircraft and 25,000 personnel are participating in the biennial Rim of the Pacific 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.