My great-uncle Hans was the executive officer (1 Wachoffizier) of the German submarine U-618 during WWII. While on patrol, the sub's activities were recorded in the log (Kriegstagebuch, or war diary). After the war, captured German naval records were microfilmed and archived by the British Admiralty, and copies are stored in the National Archives. Another u-boat researcher, Jerry Mason, was kind enough to send me digital copies of U-618's war diaries, and so I have begun to translate them.
Aside from the family connection, this project is motivated by my interests in WWII naval history and the role that intelligence and cryptography play on the battlefield. Clay Blair's books on the subject are worth a read ("Hitler's U-Boat War: The Hunters", "Hitler's U-Boat War: The Hunted", "Silent Victory"); for a great fictionalized account of cryptography's role in war, see Neal Stephenson's "Cryptonomicon".
I've found the translation to be rather challenging due the use of naval jargon, military acronyms and codes, and the occasional typographical error. Fortunately, CPT Mason's site has many excellent resources to aid in understanding a war diary.
A sample page from my translation of U-618's first war patrol can be seen here.