There isnt a single file to turn them off, each object in game has a reflection node in its corresponding .dat file which must be altered as shown in the above posts. (the dat files for ships can be found in the sea folder in your sh3 directory,)
I made a small mod a while ago to turn off reflections for the sun/clouds and a couple of the most popular uboat types, to alleviate the symptoms of an intel specific gfx glitch where the reflections would flicker and appear distorted.
The mod can be used with non intel cards too, even though they dont have that specific glitch.
http://www.filefront.com/14770399/in...ction%20fix.7z