Ditto. I've never done any of those weird "don't save too close to land, in detection range of any other ships or subs, in shallow water, within x miles of port, while not facing Mecca...."
I have saved the game hundreds of times, mostly during combat and never had a problem. I even purposely saved a game with the torpedo in the water on the way to the target and everything was fine. I don't pay any attention whatever to what the conditions are when I hit save.
One thing will make a difference. Make absolutely sure your shortcuts to SH4 point directly to SH4.exe. I'll bet 90% of corruption issues could be solved with just that change. The others could be caused by changing mod configurations and then trying to load up a game saved at sea. For certain mod changes you need an in-port save.
Keep your last in-port save always. That way you can only lose the cruise you are on. As far as all that other Silent Hunter 3 hocus pocus: fergiddaboudit!
