Having ships remain in game when sunk is a very nice thought and would add alot of immersion however, it comes with a high price.
I'll set the scene here......
A fairly long time ago, there was a gameplay/fps issue raised on the forums, where if you were hunting in & around the shallows of the coast and sinking ship then the game would nearly grind to a halt.
What was happening was the ships that were sunk in shallow water were not being completely 'unloaded' by SH3's engine and infact were still being rendered, although you could not see them. This actually affected the entire SH3 World, regardless of your position. I'm also 99% sure that it was unfixable without a SDK.
Now, as it stands, we have scripted partially sunken vessels in GWX however, it will not be possible to make your sunken victims stay around and it would certainly be detrimental to gameplay regardless of your system specs.
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