U.S. Army Chief Warrant Officer 4 Chad Trenary, UH-60 Blackhawk pilot assigned to the 25th combat aviation brigade, swims to the edge of the pool after being submerged underwater during a helo dunker simulator at the base pool aboard Marine Corps Base (MCB) Hawaii, Dec. 10, 2013. U.S. Soldiers with the 25th combat aviation brigade attended the simulator to enhance their training in worse case scenarios while flying aboard UH-60 Blackhawks (U.S. Marine Corps photo by Lance Cpl. Aaron S. Patterson, MCBH Combat Camera/Released)