I recently read Shadow Divers: The True Adventure of Two Americans Who Risked Everything to Solve One of the Last Mysteries of World War II, by Robert Kurson. It is a well-known book at this point and you may have read it. If not, you really ought to – it is fantastic. It tells the true story of a group of American wreck divers who discover a U-Boat sunk off the coast of New Jersey where no U-boat ought to be. Two men in particular pursue its identity and the story follows their tumultuous multi-year effort to prove their case. Great stuff.