Immersive techniques for the true subsimmer!

[John Pancoast]

Originally Posted by Storm501

Perhaps I didn't write my question specific enough

Why didn't Kriegsmarine U-boats submerge at night for the purpose of listening for merchant shiping on the hydrophone. Surely you can hydro-hear a darkened ship/convoy further at night than you can see it?

Yes, once a hydro contact is made and perhaps rough position/course established, U-boat would surface and race at full speed intercept course for the hydro contact, and perhaps to listen again a bit closer to check that the intercept course is correct.

Probably for the same reason they didn't do it during the day; doing so is looking for a needle in a haystack, i.e.
That's what rdf, other boats sightings/beacons, BdU info. etc. was for.