Why your batteries should not to get wet? Because water can corrode batteries, damaging them and possibly your digital camera.

If it is raining, or if you are near an area of running water such as a waterfall, be extremely careful when changing out your digital camera battery or batteries. Get a safe distance away from the water or water vapor before you do so. Water can corrode your battery or batteries, possibly causing leakage, and this can damage your digital camera as well if you insert the wet batteries.

To prevent your batteries from wet, save your batteries in a dry place..