Enigma machine found in Baltic Sea - photo

[mklotz]

Scuttling 50 U Boats, presumably in deep water and not all in the same place, would take 50 Destroyers or similar to rescue the crews. The Destroyers of course should also be scuttling themselves.

It need not be a destroyer. An old fishing boat or even a ferry would be adequate. Have it carry some small motor boats, each big enough to carry the skeleton crew. Bring in as many subs as you have motor boats, scuttle, and have the motor boats deliver the crews back to the fishing boat. Take the crews back to the sub pens and repeat as needed until all the subs are sunk.