Thats not always bad luck, you may just be running into the British Anti Submarine Patrol zones, as stated before dont take the short way home.
For example, the path south of Scapa flow is a virtual death zone for Submarines, as is the English Channel and the like.
Always go around the quick shortgun British controlled zones.
You will run into random destroyer patrols yes, but its not bad luck its just simulating how relentleslly the British patrolled around the Isles and the Channels.
They are OUT TO GET YOU.
