I have a S4 Active and it works flawlessly, you may lose the water seal but it is worth it in my opinion. I picked it up at Tmart (here)... these guys have always taken care of me(fast shipping and so on).
Here are some pictures of how it looks, I also bought the gold battery works great and has great battery life(a little less than the OEM):
If you have never seen how this works... basically just insert the module, put the back of the phone back on and toss it on the charger. Hope this helps!