Torpedoes bouncing off even when hit at 90 degrees

[Raptor]

True enough. Here are the keel depths from stock SH3. GWX has different ships, but they should have approximately the same keel depths for the same size vessel:

CAVEAT: allow for the sea state when setting running depths. Ships can rise and fall by 1 to 5 meters so it's easy to run a magnetic eel under them in heavy seas and be too deep for the exploder to trip.

small tanker...........4.8 meters
liberty cargo..........5.8
small merchant.......6.8
coastal merchant....6.9
victory ship...........7.3
C2 cargo...............7.8
troop transport.......8.5
C3 cargo...............9.0
auxillary cruiser......9.0
T2 tanker..............9.5
T3 tanker............10.7
large ocean liner...12.6


PT boat......................1.2 (don't waste your eels)
Armed trawler..............2.5 (desperation shots only)
LST...........................3.3 (and you are so close to the landing zone why?)

Most destroyers and DEs draw 2.4 to 4.0 depending on nationality and class. Set your eels to 2.0 (and pray) if you really must take one on.

Corvettes & Black Swan sloops draw 3.5 meters

CVE Casablanca..............6.7
CVE Bouge.....................8.2
CV Illustrous...................8.3
Fiji light cruiser...............5.0
Dido light cruiser.............6.3
Revenge class BB............8.5
King George V.................8.5
HMS Nelson..................10.7