Johan D...
As far as the air power keeping the U-boats submerged for a majority of their late war life goes thats pretty accurate, i mean the allies figured if they got lucky and cought a U-boat on the surface and could sink her thats great but the main purpose of the air strategy thinking is as follows
1. the allies knew that the underwater speed of the U-boats was greatly reduced
2. the allies knew that the underwater range of the U-boats was greatly reduced
3. the allies knew that there was currently no known u-boat that could stay submerged forever
4. the strategy of using ships to hunt u-boats wouldnt work because the u-boat almost always had the advantage and could either sneak in to attack or sneak away etc.
the only answer at the time for the allies was using airplanes. they were fast, they had long range, early on the only way for a u-boat to detect an airplane was to see or hear it. seeing an airplane is difficult because until it is on you it is a speck in the sky... also looking in the direction of the sound to spot an airplane doesnt always work because it takes time for the sound to reach you... planes could hide in overcast layers or even glide down onto their victims without ever being detected.
Because of airplanes, from 1943 onward U-boats rarely traveled on the surface... for the u-boats this meant it would take much much longer to reach the shipping lanes... for the allies this meant that more convoys could get through the danger zones before u-boats had a chance to arrive on station.
according to several books i have read or have seen quoted after 1943 it was virtually impossible to even leave port and cross the bay of biscay without facing several air attacks. anyone attempting to run on the surface after 1943 would literally be crash diving every few hours - an exhausting thing to have to go through - either that or they would quite simply be bombed and killed.
early in the war night time air patrols were a non existant thing, a U-boat commander could just about guarantee safe passage by cruising on the surface at night. since there were no radar equipped aircraft the pilots and gunners and bombardiers were the only source for detecting a U-boat... unless you are a flyer over the ocean at night looking for a brightly lit up party barge shooting off fireworks you wouldnt have a hoot in hell of finding anything with your naked eyes - least of all an unlighted u-boat sitting low in the water.
but two specific advances in technology made night searches possible for airplanes. Radar, which could pinpoint the exact location of even something as small as a periscope mast in a calm sea... and the leigh light which was a powerful 20+ million candel power spot light. basically the aircraft would set up an attack on the "radar blip" and when they got to within a specific range of the "blip" on goes the spot light usually shining right on a surprised U-boat crew. the fortunate thing for the U-boats as small as a fortune as it might have been was that not all airplanes were equipped with the combination radar and leigh light therfore the night searches though still lethal did not occur nearly as often as the day searches.
to get a sense of what GWX is trying to do, i think you should take a look at these estimates i borrowed from U-boats.net...
1939 - 9 u-boats lost
1940 - 24 u-boats lost
1941 - 35 u-boats lost
1942 - 86 u-boats lost
1943 - and here is where it gets rough on the u-boats ... 242 u-boats lost
1944 -250 u-boats lost
1945 - 120 u-boats lost by the first 5 months of '45
so as you can see the odds stack up against the u-boats severely after the winter of 1942 spring of 1943. and if one consideres the number of men on each boat - you could consider yourself a VAST minority to be a survivor of ww2 as a U-boat sailor.
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