In the first sixty years after the end of World War II, no one was able to find any of the 52 American submarines lost during the War whose exact locations were not already known. In most cases, the submarines were lost with all hands, and the exact locations of their sinkings were lost to history.
Advances in technology and the dedication of those who seek to explore the depths has changed all that. Since 2005, divers have discovered six sunken submarines.