How they transferred ships & U-boats from Baltic & north sea to Black sea.
http://www.1jma.dk/topic.asp?TOPIC_ID=4404
From Kiel the vessels were tugged along Elba down to Dresden, then transported to Regensburg by heavy trucks along the highways, then sailed by Danube to the Romanian sea-ports. Employing this crafty route (2400 kms), in 1942?1944 time span 6 German U-boats, 31 steamships (including 1 ice-breaker), 23 minesweepers, 50 amphibious landing barges, 26 torpedo boats, 84 patrol boats, 113 transport vessels of varying tonnage, 42 tankers, 30 tug-boats, 18 high-speed motor-boats were deployed in the Black Sea area.
Specifically considering the issue of German submarines in this theatre, one might discover that on April 18th, 1942, three U-boats of the II-b Type (U-9, U-19 and U-24) arrived to Kiel from their bases in Gottenhafen, where they were dispossessed of their accumulators, electric engines, diesels and even coning towers to enable land transportation, finally assembled again in Linz, from where they were transported by the railway to Constanta, exaclty 6 month after departure from home bases.
"transported to Regensburg by heavy trucks"
Wish I had some photos of that.