My Aunt lost her iPhone and searched the house over for an hour only to find it at the bottom of the sink. The device was off when found.
I disassembled the iPhone 4 with the help of that, hard-to-find, pentalobe bit and soaked the exposed iPhone in rice overnight. Then I carefully cleaned the mainboard with Q-tips and acetone, taking care around more corroded terminals. iPhone ended up needing a replacement part that costed me around $20, but all worked out.
Holding the Home button while plugging in a bricked or potentially broken iPhone seems to force it into a mode which allows for iTunes to restore it.
These tools are rock-solid. :)