Seehunds were supposed to go out on one-to-two day sorties. Reality was that they often lasted up to five days. Uncomfortable reality was that one sortie lasted ten days.
Some interesting details came out of Germany in a recently published book by a German researcher about the trials of various drugs on prisoners, troops and midget sub drivers. The short version of all of this was that it might have worked for a very few days. But when used periodically or for longer times there were side effects. Realilty (not in the book) was that when the Seehunds went out on sorties most Seehund drivers flat out refused to use even the uppers (amphetamines). When using the amphetamines alone some of the Seehund test subjects had experienced really wacky hallucinations. And in the book the loss of some battles were credited to the troops using the D-IX happy pills.
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a Pravda article, both in English.