Best info is of course on
www.uboat.net
That said, it sometimes needs sorting through.
Then there's the question of how definitively to identify undersea wrecks - Innes McCartney's work in academic maritime archaeology and on TV (last year's programme on Jutland 1916 for example) is a good example of how to combine the documentary records (which are often erroneous) with photos and physical examination of wrecks that have been dived.
Good luck to the 'Polish explorers' - although it's a sobering thought that the wreck could be designated a war grave, and surviving family members of the crew given some unwelcome media attention.