Well, grid AM53 turned out to be just as much as fun as I'd hoped.
Managed to sink one smallish freighter there, lol, but aside from that... the only other merchant we got a visual on may have seen us as well and reported our position because we soon found ourselves under attack by a lone destroyer while trying to take up a parallel course outside of visual range in order to overtake her.
Our only other sightings in our initial patrol grid were also destroyers, two of whom also graced us with enough of their loving attention to keep us running silent and as deep as possible for much of our time there. Thankfully "as deep as possible" turned out to be deep enough, even though 100m was about as deep as we could safely get during any of the attacks and that was pushing it.
If nothing else, ordering a crash dive and then leveling off at 70m with <5m of water left beneath the keel and a pesky Tribal class revving up for a depth charge run in one's immediate vicinity certainly gets the heart pumping!
But I must say, the ASW tactics we encountered seemed fairly lackluster; never more than one DD on us at a time, and after 2-3 attack runs they all seemed to lose interest and move on, or lose track of us entirely judging by all the ashcans exploding further and further astern of us as we made our escape. Not that I'm complaining!
Only once did they get near enough to cause any damage, and that was the one time when we were in water just deep enough to get the repairs done and still stay clear of additional punishment until going silent again.
I took some shots at the DDs when I had decent position and range before getting detected and/or going deep, but if any of them hit at all they were duds or else the Tommies saw them coming and their evasive maneuvers proved more effective than their subsequent attempts at destroying us. Six months ago I could run at p-depth and lure a distant DD into giving chase and then blow it out of the water with a well-timed stern shot - but not this time. They are getting smarter in that respect.
No aircraft, though! Which was kinda surprising. But we had very little clear weather while in that close, so maybe that explains it. I did expect a little love from coastal command, especially when it seemed like our position had been reported.
Our one success in AM53 was with a hydrophone contact we picked up while patrolling the western edge of the grid; a second sound contact pulled us into AM52 where we had another sucessful attack. At that point we had two eels left in the bow plus our external reserves, and since the weather seemed to be in a cooperative mood we headed further out into the Atlantic in the hopes of getting the externals transferred without undue harrassment.
No sooner had this bit of housekeeping been accomplished than we got report of a convoy heading, no doubt, for the upper Western Approaches; their reported course had them running NNW, almost directly into our path. As we turned south to find them ourselves the weather turned foul; by the time night fell and we were nearing our projected intercept point, the darkness and driving rain had cut our visual range to 2km or less.
Submerging to 40m and checking the 'phones we found we had indeed come very near the starboard edge of the advancing convoy; the lead escort was already several km north of us, the starboard screen had been well and truly penetrated without our even having tried. We got a read on the ships in the nearest column, came to periscope depth, and turned slowly into attack position.
I could barely get a visual on the ships about to cross our path, but was finally able to make out three of them - two smallish freighters and, eventually, a much larger vessel coming into view behind them. I fired one eel at the second of the small freighters, and then waited for the larger prey; that one got a spread from the last two available fore tubes. All three eels hit and detonated as I turned hard to starboard, waiting for any indication of response by the escorts and preparing to point my stern tube at the column should a parting gift be required.
The smaller target didn't require it; we'd hit something vital judging by the series of explosions that soon followed the eel's detonation. The larger vessel slowed a bit as we continued to shadow the column, and small fires could be seen here and there on deck, but aside from slight list she was still making way although turning gradually to port. Unfortunately her slow alteration in course was also bringing her right into position for the parting gift I'd been contemplating. The third eel sealed her fate.
By then the escorts had begun a slow if sure convergence towards the scene of the crime, but by the time they got within anything resembling visual range, we were diving at flank speed on a course that would put us directly underneath the rest of the convoy. We never heard so much as a ping from their ASDIC. We leveled off at 120m and went silent, listening on the 'phones as the entire flock made the turn east towards Britain and home. A couple of escorts stayed behind for short while, circling the attack location in ever-widening orbits and, once the columns were clear of the area, forlornly dropping ashcans in a section of ocean now thoroughly devoid of u-boats. When they gave up and left to rejoin the convoy we slowly returned to the surface, fired off a report to BdU, and began our own long journey home.