For decades, the U.S. military has maintained its dominance in the depths of the world's oceans by boasting the most technologically advanced submarine fleet.
However, officials say China and other nations are rapidly expanding the size and scope of their own submarine forces. And, according to a report by the Center for Strategic and Budgetary Assessments, the U.S. must rethink the role of manned submarines and prioritize new underwater detection techniques.