[Bilge_Rat]

for the torpedo man, there could be an ability to reduce dud rates/increase accuracy. Torpedoes require a lot of ongoing maintenance and unless they are kept finely tuned, they could easily go off track (i.e. runs too deep, can't keep correct gyro angle).

for the sonar man, his ability to detect contacts would go up with his skill level. It does not appear in the game, since sound contacts are very noticeable, but in RL, sound contacs may be very faint and hard to distinguish from the background sea noise. A good sound man can make a difference.