Large Tanker picked up on sonar, spent close to 45mins real-time setting up for the perfect shot, all dials tuned-in, range calculated and Gyros set...and at 500m I spot the swastika..
She almost deserved to go down for doing that to me.
Hit HMS Nelson with 4 torps in THICK fog, (visibility 200m), had to dive to evade DD's, when I surfaced, no sign of the convoy, and never picked up the scent...