U.S. Marines with the 31st Marine Expeditionary Unit fast-rope from a CH-46 Sea Knight helicopter during visit, board, search and seizure training aboard the amphibious dock landing ship USS Tortuga (LSD 46) in the Philippine Sea on Nov. 16, 2009. The Tortuga is part of the USS Essex (LHD 2) Expeditionary Strike Group, which is participating in Annual Exercise 21G, a bilateral exercise conducted by combined U.S. forces and the Japan Maritime Self Defense Force.