Apple's iPhone is a technologically advanced smartphone capable of accessing the Internet and email and running a wide variety of applications, both Web-based and otherwise. Like with most other electronics, however, exposure to excess humidity or submersion in water can spell disaster for the iPhone, damage which may or may not be fixable.
If your iPhone gets wet -- for example, you leave it on a windowsill during a rainstorm or it falls into the toilet -- the first thing you must do is power it off, even if it seems to be functioning fine, as it may. Allowing electricity to flow through a wet iPhone further damages it circuits, lessening the chances it will be repairable. To turn off your iPhone, hold down the round "Home" button and the oval button on top of the device at the same time; then slide the bar that click "Slide Here to Power Off."
In some instances, it may be possible to salvage your iPhone simply by drying it out. Perhaps the simplest method of doing this is to place the device completely inside a bag of uncooked rice, which draws out all the moisture from it over several days. Another way to place the iPhone on a metal sheet or tray, then set the tray above a 40-watt light bulb. The slight heat from the bulb -- and the conducting power of the metal -- accelerate the iPhone's drying.
Things to Avoid
Obviously, in order to test whether or not you drying has been successful, it's necessary to attempt powering the iPhone on -- or, if a lot of time has passed, charging. It's important to note, however, that if your device doesn't power on within the first five seconds of you applying power to it, you must remove the power source. Again, electricity flowing through a water-damaged device is harmful to its circuitry. If your own drying attempts fail, do not attempt to disassemble the device yourself.
Water damage to your iPhone is not covered by its limited warranty -- and the Apple representative to which you take your device, if you choose to have it repaired in-store, will know about the water damage, even if you don't tell him. The device is equipped with a water-damage sensor at the bottom of its headphone jack, which turns red or pink in the event of exposure. When seeking repair on a water-damaged iPhone, get quotes both from Apple and from third-party providers, as the latter may be cheaper.