Have to disagree here as I once dropped my DIAD in a deep puddle. The DIAD was completely submerged but it worked fine after I hauled it out and wiped it off.
I never said you couldn't get lucky, but I wouldn't take that chance. Symbol does deny warranty claims for water in the board. I've seen it done. I'll keep mine dry, you do whatever you want with yours. Just make sure you come back and tell me how much they take out of your check when you're not quite so lucky.