Sometimes I exit and save, put in something like convoy, submerged just as a reminder of what was happening when I stopped and saved. Every now and then it will say 'game not saved' or something like that. If you are not careful you can click the OK button thinging it was saved when in reality it was not. I have done that twice. It sucked as I had a lot of tonnage or had a great convoy position etc. Watch for this when saving.
