Crept in along the bottom, keeping towards the S side of bay, while the SSN also came in closer to reduce Tomahawk flight time if necessary. Occasionally stuck up the ESM mast, but kept getting hits from an airborne radar so stayed down most of the time. Bumped into an underwater friend at very close range, fortunately able to turn onto a passing course and get into his baffles, and then (in a lapse of mission discipline) decided to torpedo him, giving a nice 'here I am' sign to the foe. Hurried to the S shore to break contact (while watching batteries drain...) and somehow managed to avoid any other contacts. Crept east through the shallows (less than periscope depth at some points), and delivered boat successfully.
I decided to keep playing after that, to see if I could get out past an alerted enemy now that my batteries were half gone. Retracing my course got me an ESM contact on a corvette, so made a radio call to the SSN, and shortly thereafter heard the pleasing ship-shattering Kaboom as the missile met the corvette. Crept out afterwards, trying to snort at night, but still getting forced down by airborne radar, and wasn't able to fully recharge until well out to sea.
Looking at the saves after the game it turns out I got really lucky after engaging the enemy sub, and managed to inadvertently slip through a gap in the sonobuoys they were laying to look for me, so it probably would have been wiser to break contact and let him go. I probably brought the SSN in too close as well, since it was actually inside the edge of the enemy's sonobuoy pattern at one point. Most alarmingly, looking at the expenditure logs it turns out they even fired a torpedo at something at one point, and I never even heard it. So much for my situational awareness!
Maybe consider making the escape part of the scenario as well? With batteries partly depleted and the probability of foes in your path it is an interesting situation.
(A couple of typos: in the side briefing "Although egger to be rid of them..." should be eager. In the On the Beach message Broadsward should be Broadsword.)