Well... I tested this, and only by accident. I dropped my SGS2 in a pail of water yesterday... after 1/2 second of shock I pulled it out and frantically raced to remove the back cover so i could take out the battery, all the while the screen is going crazy and the phone is making weird sounds from the speaker. I got the battery out but I was horrified, about what I had done. I went to my car and turned on the engine, and set the dash heater and fan to full then placed the disassembled phone over top of the vent. I had to have a cigarette to calm my heart that was beating a mile a minute. After the smoke, I carefully reassembled the phone and turned it on. After a second I saw the boot screen, oh thank god! But then, I noticed no boot-up sounds and then the home screen never appeared; my heart sank, what had I done? I looked closer and saw that the front camera was still completely fogged over with moisture. So I disassembled the phone once more, taking out the battery and all the cards and again put it upon the dashboard heater vent. I left it there for about while I went back to work inside. I tried to work, but all I could think about was my $600 dollar ruined phone. After 45 minutes I went back to my car to check on the phone; I picked it up and it was so hot it almost burned me! Oh no, have I made things worse now I thought to myself. I let the phone cool off for about another 15 minutes. Finally I put the cards back in and then the battery... I was scared to turn the power on, as if waiting would make a difference, I powered on, and got the boot screen, then I heard sound, beautiful music to my ears, and finally the home screen! Oh what joy I felt; I quickly tested all the functions of the phone, speaker, microphone, sdcard, wi-fi, cell reception, usb connector. Everything checked out fine.
So to answer the question, the SGS2 passed the water test and the heat test, well at least in my case lolz... I wouldn't recommend it though, and I'm sure Samsung wouldn't either, but boy am I relieved my favorite toy survived...