A Royal Canadian Navy explosive ordnance disposal sailor from the Canadian Fleet Diving Unit-Pacific adjusts his helmet prior to boarding a U.S. Navy MH-60S Nighthawk helicopter from Helicopter Sea Combat Squadron 4 during Rim of the Pacific Exercise 2012 fast rope training July 16, 2012, at Marine Corps Base Hawaii - Kaneohe Bay. 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 worlds oceans. RIMPAC 2012 is the 23rd exercise in the series that began in 1971.