I know this mod just released and you are working on it, but this is what happened when I dropped the submarine from a bit of height to water and did it again trying to CRL + R at the right time, then this happened.
I know about this: I have tried fixing it but my attempts only resulted in it worsening, currently it's the best I can do.
*BUMP, SORRY* haha kosatka go brrrrrrrrrrrr also, if you can make a full blown submarine mod, i assume you could make something like, oh idk, a submarine bolide maybe with inspiration from a certain 1970's spy movie? (also just take this as a suggestion, this is probably 10x harder than making the la class sub)
Have you ever tried shooting the missiles at the people on the flying bikes? Great sport here in America