" It booted, but the fans blew at full speed and it shut itself off while still running firmware."
This may be unrelated to the water damage. It is very common with high spec laptops that the fans get filled up with fluff and then overheat. It is a good idea to open up your laptop once in a while and hoover out the fluff. Or wipe it away with a clean, dry toothbrush. This is a problem I often had with a laptop that I had with coolers, fans and a high end graphics card a few years back.
You can tell if it struggling if you hear the fans running a lot, and the base of the computer gets hot. Cleaning out the fans can give your laptop a new lease of life.
If you had been able to turn it off right away, and put it in a bag of rice, I have seen that work for some people, at least for a limited time. There are claims out there of various methods.
But if the screen is bad, at minimum you have to replace that, that's virtually certain. You don't say what model it is, so not sure whether that's possible or how much it might cost.
Try the rice thing for a few days, you have nothing to lose at this point. When I used to take calls for Applecare I had several customers tell me this worked, the idea being the rice would suck the water out. I don't believe it's really a great idea but it can't hurt at this point.
Having said that, your phone is pretty much toast, per the other answer. When I was lent out to the Apple store, we saw Macbooks and phones come in where the customer said they had "dried it out" but "it wasn't working" a few weeks later.
Invariably we'd open the thing up and see some residual water in there.
Sorry to say, you are probably on the road to a new phone. :( Now if you try a third-party place to repair it, at least the last time I worked for Apple about a year ago, if you put third-party parts in there Apple will never touch it to do a repair. Unlike Macs where you don't "void the warranty," any third party parts in an iOS device precludes Apple from doing any repairs in the future.
So balance out free (rice) vs. third-party screen (cheaper) vs. shiny new iPhone 6S!!
To clarify a statement above, with Mac products, if you add a third-party hard drive, for example, or memory, PROPERLY, without damaging anything in the process, you can still take your Mac to an Apple store for service and warranty.
Again this was a year ago, the last time I dealt with it, but if an Apple Specialist or Genius opens up an iOS product and sees a third-party screen or battery, etc, they immediately stop working on it, in most all cases. You'd be amazed how fine an eye these Geniuses have for sniffing out third-party screens -- so I'd only go third-party (non-Apple) parts on something that's out of warranty.
Best Answer
The reason it's brighter is because water has a refraction index that is closer to 'glass' (as in the specific material used in the screen--I know it's not really glass per se) than air does. This means that less light is lost in the area between the LCD and the front glass (or between the LCD and the backlight--but not very likely) and thus the screen appears brighter.
You'd probably get a better explanation on Physics in terms of specifics, but this is the answer in a nutshell.