170915-N-SH284-087 KEYPORT, Wash. (Sept. 15, 2017) Members of the Bathyscaphe Trieste Alumni Association tour Naval Undersea Museum-Keyport during their bi-annual reunion. Trieste is the only manned submarine ever to explore the deepest part of the ocean, the Challenger Deep in the Marianas Trench. Trieste II, the first deep submergence vehicle built by the U.S. Navy, following its acquisition of the original Trieste bathyscaphe, is permanently on display outside of the museum. (U.S. Navy photo by Mass Communication Specialist 2nd Class Vaughan Dill/Released)