hey d00dz, i can help you out with this one. =P
OK!
almost every phone thats been in water can be fixed, within reason. (washing machine/ sitting in salt water for a day is NOT reason)
if your crafty like the ninja you can fix it yourself.
need:
distilled/demineralised water (from supermaket)
methylated spirits, (also from supermarket, cleaning section probably)
some luck
first thing is to get it out of the water asap and get the battery and sim card out. the longer power is on it while its got water in it the more chance that something will short out inside and cause it to die in a fire. if you dropped it in salt water (oh gawd) its still fixable, but youll need to remove as much of the casing as you can such as battery cover and the whole case if its one of the ones that you can change the case on (like when you buy pretty pink ones from that chinese phone place). youll then want to wash it out with distilled water/ demineralised water, get it from any supermarket (do this for pools, puddles and any others too. to get out any bits of dirt and salts in there) after youve sloshed it around well and rinsed thoroughly, (leaving to sit for awhile even if it was in salt water, then sloshed and rinsed again to get it all out)
then you will need the metho, which is just ethanol (the stuff that drinkies have in them, only 99% per volume) with some poisonous icky bad tasting stuff so kiddies/hobos dont drink it.
try and dry off as much water from the phone as you can. towel, shaking or whatever works for you (oven not recommended, lest your screen suffer a potentially horrible fate) doesnt need to be really dry just so its not sloshing.
next you need to get a container, (bucket is good idea) put your phone in it and pour in enough methylated spirits to cover it. then move it around abit to get the metho all through it.
the basic idea here is that ethanol (ie methylated spirits) and the water left in your phone will combine, ethanol evaporates at a much lower temperature then water and also does not conduct electricity (good thing). you may then warm your phone up and the water will evaporate with the ethanol leaving you a nice, water free phone.
you can now chuck the battery back in and see if she works! it is possible that there 'may' still be water in the screen, as theres lots of little bits for it to get into in there, youll just have to try and rinse that really well and dry it. nice n warm, so you can still touch though (those damp rid things that suck the water out of the air into the little bucket could be a good idea, or even rice)
the reason it is important to wash it out "thoroughly" with the pure water first is the salt and such obviously wont evaporate, which could mean bad things (such as dodgy keypads) and corroding circuit boards.
IF it still isnt happy after all this, you may wish to repeat, as water/ gribbly bits may still be in your phone making it unhappy. but if you get it all cleaned out and dry its its all but guaranteed that it will work again.
lame-o phone techies not taking water damaged units, just cause it takes more time then they get money
but the 10 odd bucks thisll cost you can save you a couple hundred of a new phone
edit: yes, while your warranty is void by water you can still get it fixed, though at your own expense.