I read the comment from pollytintop, and I agree.
The proper "rules of engagement" for approaching and fixing water damage involve the complete removal of water and assessment.
Sadly, this implies dismantling the water damaged device.
Water itself isn't damaging: electricity is. And water reroutes electricity in every point of the iPhone where it's not supposed to go, thus, wrecking havoc with the water logged device.
A lenghty stay in a [product|IF145-163|Thirsty Bag], or, lacking that (and only if you can't afford getting one, I'm listing the possible avenues in order of efficiency) a cup filled with silica bags in a dry cupboard , or, failing that again, a cup filled with rice in a dry cupboard is always a good start.
Then comes the dismantling: open carefully your device. You'll need a special screwdriver, included in [product|IF182-019|this kit, along with two new, philips headed, screws]. Be careful: the iPhone 4S is filled with little, tiny parts.
Follow the guide for battery replacement: you're surely going to need a new battery, as yours was shorted up, and it'll always get a really short life.
Since you're there, clean everything with isopropylic alchol, keep everything dry, remove traces of weird corrosion, or even fungi (but be careful).
Then, close everything up and reassess.