Or do you feel it is your duty to throw caution to the wind and try to sink everything in sight? Then you will likely have a short but glorious career.
Do you want to see if you and your crew can survive the entire war? Then you may circumspect in the risks you take.
You are a a WWII U-boat commander with a career played out in a completely dynamic campaign in which you can decide for yourself what defines success. Silent Hunter 3 is as much as an RPG as it is a sim.