There were so many hundreds of false sightings and reports of such activity in the First World War that I am not surprised the tradition of looking for them carried on. My impression of the WW1 'U-boats everywhere' problem was that it was caused by three things:

1 The exploits of Allied subs in the Sea of Mamora proved how an audacious captain could use this new weapon,
2 a lack of understanding of how submarine craft operated by those who were assigned to guard against them, and
3 a few early, probably authentic, cases of German U-boats poking around harbours in the Med.

The rewards offered by British and French intelligence for information certainly played a big part in the Med.

None of those three factors applied to WW11, and, as pointed out by everyone else, there really wasn't a good reason for a Captain to take the enormous risk. Popping up just long enough to drop/collect an agent maybe, but not prolonged surface activities.

Barry,
Well said, but just a detail:

'...not one Irishman fought for Hitler.'

This doesn't include William Joyce, aka Lord Haw Haw. He tried his best to avoid prosecution for treason after the war on the grounds that he wasn't British, he was Irish. As I understand it, he had a good case too, and was finally nailed on an obscure point: in the '30s he had obtained a Readers Ticket for the British Library and had given his nationality as 'English'. As I am sure you know he was tried and hanged at Wandsworth Prison on January 6th 1946.

Best regards,

Bruce