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^Moreover as shown in Das Boot a considerable amount of greasing the eels was necessary to insure the air pressure release of an eel. http://digitalcommons.georgiasouthern.edu/cgi/viewcontent.cgi?article=1599&context=etd Required reading! pages 153 &154 especially the pressure issues inside torpedo tubes affected the poor depth mechanism. Moreover the tube open and the sub downward could cause an eel to slide out of the tube partially at which the bow would be elevated to cause it to slide back in.... always a precarious situation. http://uboat.net/forums/read.php?20,87333,87621 "

A torpedo stuck in the tube was a different problem but there were things they could do to try to free if the compressed air wasn’t enough to force it out of the tube.

There was a manual procedure to force out a torpedo that was stuck in a tube that involved using the mine ejector mechanism which injected the compressed air directly at the rear of the torpedo instead of behind the piston but most stuck torpedoes got stuck in the first place because one of the cables that were connected to the torpedo while it was in the tube didn’t retract when the launch was initiated and if it couldn’t he sheared off by compressed air it presented a serious problem. The outer torpedo tube door was open when the launch was initiated and if the torpedo moved far enough forward during the launch the outer torpedo tube door couldn’t be shut and the inner torpedo tube door was the only thing keeping water out of the boat and it wasn’t strong enough to do that at great depth so it rendered the boat somewhat crippled. The inner torpedo tube door couldn’t be opened so that something could be used to manually push the torpedo out either. The bow of boat could be dipped such that the considerable weight of the torpedo would aid in its sliding out of the tube but if that didn’t work the only way to get inside the tube to work on it was to surface the boat so the inner torpedo tube door could be opened and even then the “fix” given the limited room inside a torpedo tube might well have been beyond the capability of the crew at sea. Alternatively the bow could have been raised to use the weight of the torpedo to slide it back into the tube so the outer door could be shut but sliding a torpedo around inside the tube was also quite dangerous."

Salt water in an open torpedo tube, essentially a thru-hull weak-point, especially under water at depth(pressure) are mutually opposing concepts; the briny sea is nothing's friend. Gaskets, grease and temperature sensitive eel (eto) batteries are especially vulnerable.