Der Teddy Bar designed the NYGM mod - here is a sticky describing it better than I can:
http://www.subsim.com/phpBB/viewtopic.php?t=50331
Basically though, it does two things: it makes ships sink cooler and it makes them impossible to sink with the deck gun. Check out the thread.
And if you download NCOT 1.1, you will find both .zon files included.