FishingSound enhances your sound settings during the small periods of time that fish are caught during the Fishing cast.
Sound will be enabled if it's disabled, Sound Volume will turn up, and other unnecessary noises will be muted. This only happens during the small periods of the Fishing cast when the bobber is expected to bob.
The easiest way we have of knowing if we have caught a fish, is by the little 'splash' sound.
However, if we usually play with our sound turned down, or off, then it's annoying having to turn our sound up or on just so we can more clearly hear our fish splash.
Personally I always fish while watching a movie. This means that WoW is in the background (can't see the splash) and I have the sounds of the movie to content with. With this addon, I can watch my movie, keep WoW in the background, and clearly hear when I've caught my fishy.
There are two lines at the very top of Core.lua
local SoundVolume = 1.0
local MasterSoundVolume = 1.0
If the volume is too loud, reduce these numbers a little bit