The rice trick is the best for small electronics and it does work miracles. As stated, get the batteries out as quick as possible.
Then put it in a bag of rice overnight(ziplock baggy or a freezer bag sealed tight). You want the rice to pull all the moisture out of the device and not have a chance to pull it out of the air if you leave it unsealed.
Will dry out cell phones, ipods, etc.. and i would assume garmin handhelds.
I wouldn't suggest leaving out in the sun, as it could actually cause some heat damage.
I haven't dunked my garmin yet, and hopefully won't have to use the rice bag on it any time soon
Maver!ck
