difficult comes after 1942 i think... interesting situations on the other hand.
On a recent patrol i was running on the surface in a heavy squall recharging batteries after running submerged for a length of time.
suddenly ahead of me about 200 meters off my port quarter a massive shape emerged from the fog. It was a British merchant. there i was in a very low traffic area of the mid-atlantic and there is a single merchant damn near colliding with me!
stranger yet. he never saw me. Perhaps his lookouts were busy huddling under their pea coats and rain coats for warmth? I went hard to starboard and estimated his speed to be 5 knots.
took a snap shot from about 400 meters range (point blank) and hit him dead center.
sailed up to the two life rafts to simulate dispersal of 3 cans of beans and a gallon of fresh water, then sailed on.
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another time i stumbled upon a heavily escorted convoy, in the center was the HMS Rodney fired a spread of three at the BB and two missed astern, one struck under the screws immobilizing the ship.
I went deep and evaded the DDs. over a 2 hour span
in real time i stopped counting after 80 depth charges
they went back to the convoy and i hit the rodney with two more eels sinking it.
stalked the same convoy for three days, picking off the largest targets and repeating the evasion. I think - though i would have to look back - i sank 2 whale factory ships, an ammunition ship and a large tanker from that convoy over the three day engagement.
the ammunition ship exploded in a furious way. I would assume all aboard were killed instantly. There was hardly surface debris. a couple of life rings and an empty life raft was about it... not even a single body remained afloat. stuff like that makes you sit back and think that for some folks - this was no game... this was a reality for them.
headed to the belchen supply ship and then steamed home with no further contacts