Fishing in World of Warcraft involves casting and then waiting for the fishing bobber to move, which is accompanied by the sound of water splashing.
I used to use a modification that disabled all of the casting sounds in World of Warcraft, which consisted of replacing all of the associated game sounds with silent files, stored in a folder called 'Sound' within the 'Data' folder - so I imagine that this is possible, but does anybody know how to change the water splashing sound that indicates you've caught something?