Come to think of it, the one I did find and sink was just north of Scotland, was early on a day after I sank the merchant. Then I headed northwesterly and got into even rougher seas.
Then BDU repositioned me even further north, what do they know though.

Seas are getting less rough the further south I go, that'll help if it holds.
Well we be headed back south now, about 24hrs away. I bet I can catch them out farther in deeper water, that was where I found the other one.