The best way to deal with a device that can be disassembled (as the V20 can) if this happens is to:
1. IMMEDIATELY remove the battery. That's the first and most-important thing! DO NOT EVER POWER IT BACK ON UNTIL YOU'RE CERTAIN EVERYTHING IS DRY.
2. If salt water, you're hosed. Give up. Seriously, the odds of success if the water is brackish or salt (that is, ANY salt content) is nearly zero. The reason is that just ONE high-voltage (e.g. power supply rail) line that gets bridged to a logic line will fry whatever that other chip is, and you're done.
3. If FRESH water you have a chance. Disassemble as much as possible. In the BEST case you can get the mainboard and auxiliary boards out. Do so. Then rinse all the *disassembled* parts in 90% or better (100% is best if you can get it, but it's not easy to get) isopropyl alcohol. Use plenty of it -- what you're doing here is getting ALL the water off, to the extent possible, that may have any mineral content in it (that's what causes the shorts and makes things fail.) Be careful with things that are precision and unsealed (e.g. camera modules) as if they didn't get water in them and you flood them with alcohol it may not dry out, and if it doesn't you'll ruin them -- close inspection is necessary on those first.
4. Use "canned air" to blow all the alcohol off as much as possible, then set the board(s) in a warm, dry place and let them airdry for AT LEAST 24 hours. Air from a scuba tank (-50F dew point) with an airgun attachment for the BCD hose works too, but DO NOT EVER use air from an ordinary air compressor (the air from them is both moist AND, for most units, oily as well!) There WILL be residual alcohol in crevices, and maybe some water, you cannot get out with the canned air -- this is where the risk is, because the minerals in the water are (again) what creates the short circuits and ruins things.
5. After at least 24 hours CAREFULLY inspect with a jeweler's loupe or other means of moderate magnification to check for ANY moisture or obvious burn or mineral-tracking marks where shorts occurred. Pay particular attention near and under the pads where ICs are soldered and around other things that can trap moisture. If it's not completely dry wait longer. PATIENCE IS A VIRTUE HERE. If you see mineral or burn marking you're probably (99% of the time) screwed.
Put it back together and try it. If you got lucky and there was no short while the battery was in it, most of the time you will have success. If you tried to use it while it was still wet, however, even momentarily, the odds are extremely poor.
Rice does very little. If you're in fresh water and have no other options, or if any sort of time has passed, a better choice than rice is to either find a nice, hot car (temp <150 but over 100F) or a heated chamber of similar temperature (set to 120F if you can) and place the entire unit in it opened up as much as possible. This will drive the moisture out but it will take several hours to do so, depending on how wet it is. IF you have suffered no shorts this will probably be effective, but it leaves any mineral deposits in the unit, which means the risk for future trouble is quite high. Nonetheless if you can't get the boards out to flush them properly with a chip and solder-safe dessicant (e.g. isopropyl alcohol) it's a better bet than a bag of rice.
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