If you want to believe wiki a gato sat 17 feet deep in the water and a fletcher 17.5. Sounds about right. And I think many IJ smaller ships drew far less but still sit on the bottom. I think the magnetic detonator was off by the end of 43 after many US skippers had run their own tests showing the things were not working. Germans had the same problems at the beginning of the war, but ditched them quickly, which was unfortunate for many, many Allied seamen. And a bit of an afterthought. The recently found Eagle had a draft of 8.5 feet and the German sub had no problem sinking her.
Two stories come to mind. One where a US sub crippled (I think) an IJ tanker and then proceeded perfect set-ups for something approaching 20 more shots. The results were horrid. For the USN that is. The other is borrowing fishing nets in the HI and firing torps into some cliffs. The holes in the nets showed that the torps were running - at best case 10 feet deeper than set. Now that has nothing to do with the magnetic issue but US skippers were blamed for the early war failures when in reality:
torps were running deep
magnetic detonators were not working properly
firing pins bent and did not explode on a straight (90 degree) hit because they bent. Only non-perfect, off angle hits worked.
Trying to solve a multi-headed problem is not easy as any developer/computer programmer will tell you so this was hard to solve.
TO make things even worse, before the war, in order to save money, practice firings were carried out with torps that were easy to recover for 'cost saving' reasons. This meant the torps had a different warhead weight than what 'live' warheads had and made all the data a bit wonky.
And to top it off I think I recall some of the top brass in the sub force in WW2 were involved in those Newport test firings and refused to believe there was anything wrong with their precious product - must be the skippers. I cannot recall which of the senior brass it was - but admiral level.
The fact that the Dolphins were able to do what they did under that backdrop makes their accomplishments even more impressive.
Well said - the story of the "we crippled her, I'm going to keep shooting until I sink her" (actually a whaling ship) is well told here:
See 24 July '43.
"In all, USS TINOSA fires 15 Mark-14 torpedoes and gets 13 hits, but 11 are duds."
I have yet to master the combination of settings, patrol zones, and captain selections that allow one to replicate the lethality of the late-war US sub force, but judging by some of the AAR's out there it can be done.