Use the variable damage boxes mod to allow listing/stem/stern-up sinking effects? Where was that mod? Nice oil slick?
Can depth charges actually explode under water (with a delay, and use the big plane-crash splash, never tried them..?)
Since there are no evasive reactions in the ship AI code, and they can only blindly follow waypoints, what if they could go through a surfaced/periscope depth/deep dive LOD model cycle?
(Deep is the longest phase, and they would have to disappear somehow, extreme LOD model reduction? Some way to reverse this at night so they are mostly on the surface?)
Can a dummy plane spotting AA routine be used to trigger a model change (dive)? Players would have to spot, reach, and attack before they went down deep again, so they can possibly escape even if stuck going in a straight line.
Anto said the ship AI is 100% dumb and can't be changed, so any AI aspects are probably out of the question, but it would be enough to have to just spot and hit them, but would planes carrying depth charges need any special AI routines?