In case somebody is interested in the WW2 stuff about schnorchels and radar I recommend reading this:
http://www.militaryhistoryonline.com...tic/uboat.aspx
It says there: "The "Schnorchel" device could sometimes be detected by radar or keen-eyed lookouts in calm weather, but although virtually impossible to spot in rougher conditions, these same situations often caused problems of their own."