If dropped in salt water, it's a goner for certain. Contact your insurance company.
If dropped in fresh water, it might still work. But it depends upon how much moisture got inside and a bit of luck.
1. Remove the battery. Important. Do this first. You want to remove power sources in hopes of preventing electronics from shorting out.
2. Turn off camera. Remove the memory card.
3. Remove the lens (optional, see below).
4. Leave open battery compartment and memory card compartment doors to help air out inside.
5. Pop up the flash and leave it standing open.
6. Remove the eyecup and set it aside temporarily.
(Note do not remove lens or open up this way if you sit the camera in rice. You do not want rice dust getting inside!)
Let sit for some days to dry. Do not put the battery back in and turn the camera on until you are certain it's completely dry.
If the lens got soaked too, then it's going to be harder to get dry inside and likely ruined. Try leaving the caps off and standing it on end to dry. But it's still likely to end up with stuff dried onto the optics inside, at best. At worst, it will develop fungus or mildew inside. This can happen inside the camera, too.
Most repairers won't even look at a camera that's been dunked in water. They too often simply aren't worth trying to repair. To be done right would require complete disassembly, cleaning and relubrication.
But it costs little or nothing to try dyring it yourself.... after you get it completely dry, if it's still working okay it might be possible to have the focus screen and mirror cleaned, if that's needed. Don't try to clean these yourself. Both are very easily damaged by the wrong cleaning solutions or incorrect procedures.
I've never had a camera get dunked in water... but have gotten caught in heavy rain with cameras, lenses and flashes... I followed the above procedures (no rice, just warm air from a hair dryer) and everything survived and continued to work fine after a few days drying out. There was no sign of water inside the cameras or lenses, though.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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