Dear Roberto,
the German midget submarines were intended for use against landing ships and their escorts, but they could not fight in rough sea. Northern Adriatic was a possible target for Allied landings and usually is a very calm sea. Sistiana bay, near Trieste, was a midget base submarine from 1943 to 1945 and remains of the facilities are still on site.
Professor Enriquez collection of war material and memorabilia contains two midget submarines; they are on exhibit in Trieste, in a place called “Museo della guerra, per la pace”, hosted in some former barracks.
Greetings
Walter M.