Does anyone know any of the following?:

1 What is the minimum depth of water in which a U-boat could operate? For example, how close into the shore a could a U-boat go when involved in clandestine operations to land an agent on a hostile shore?

2 What is the turning circle of a U-boat? If operating in shallow waters with many sandbanks, how much space would a U-boat commander feel he must have in order to be able to turn his boat?

3 Where were the U-boat bases before the fall of France? Are there any records of U-boats operating in the southern North Sea at this period?

4 If landing an agent on a hostile shore, what kind of dinghy could/would have been carried on a U-boat? Would it be an inflatable? If so, how big? What colour? Would it be conceivable to strap a wooden dinghy to the deck of a U-boat?