Things in SH3 are not always as they appear.
Several times in GWX, I've fired two torpedoes at a motionless vessel only to receive the dreaded "Torpedo missed, Sir" message for each one, which is strange as I know the depth setting was well above keel level and the sea state was calm.
Visual examination shows no fire, no smoke; just a sitting duck with its feathers intact.
A few minutes later, I get the "She's going down" message and the vessel sinks.