You can test this by setting the maximim depth in the sub files.
AFAIK if all depends on buoyancy and recovery form any damage is detemined by depth and speed.
I've had a situation in SH3 where I had to increase my speed to stay buoyant, and compressed air made little difference. This was a catch-22, as the escorts could track me and they pummeled me to Davie Jones.
SH4 is the same engine as SH3 probably with some additions.