Flag, yes there is a file. I don't know which one it is. If nobody has given the right answer yet, I'm assuming it's not a well known file. Do a search for "decks awash". I remember once somebody mentioning how to change the file. Actually check the newbie guide, button thread, one of the stickies at the top, somebody says how to assign the ; key from snorkel depth to decks awash. That may lead you in the right direction.
EDIT: try this:
http://www.subsim.com/radioroom/show...1&postcount=41