In December of 1941, a British Submarine was patrolling the Mediterranean Sea off the coast of Greece when it struck a mine. Immediately, the explosion caused the sub to take on water, and the 61 crew aboard sank to the bottom of the ocean, but something curious happened after it touched down on the ocean floor. Something so rare and almost impossible, that it wasn’t believed for a long time afterward. And, decades later, the sub’s whereabouts still remained a mystery until a planned expedition in 1997. When the wreck was finally located and the truth was finally learned, it would completely change everything. This is the sinking of the HMS Perseus, and as always, viewer discretion is advised.