Partial damage is modelled for subs as well as surface platforms.
This can happen when you get hit by a weapon whose power does not exceed ownship damage capacity, or if the blast is some distance away from the ship.
How common an occurance this is can be controlled in the database, but it should be fairly rare, since a damaged sub is almost as good as dead in terms of playables.
In the LWAMI Mod, some torpedoes have very light warheads to simulate either very light torpedoes are ones known to proximity fuse so these will cause this to happen, and the Oscars and Typhoons have also been beefed up to require multiple LWT hits to completely take out. This is kind of an approximation. No one who can talk really knows what happens when a half a cubic foot of high explosive impacts an object that weights 15000ton or more under 300m of ocean. :hmm:
My gut tells me that even a double hulled russian missile boat is toast from a LWT at 300m, but something also tells me that it might be possible to sustain such a hit. We kept things simple by keeping all playable subs killable with a single playable torpedo, except for the Chinese SET torpedo, but then again who is going to kill anything with a 29kts torpedo?