At work I keep a spare battery in my pocket, don't want to be without. At least twice I have put batteries in the washing machine inadvertently and both time I check them on the charger and they have been fine. I have done it with flat ones and fully charged as well. They have always been fine which surprises me as water is great conductor but I have noticed not a single problem with them at all they hold their charge as if nothing had happened.
I do visually inspect them for leeching but haven't seen anything out of the norm apart from a little rust spots that scratch off.

On a side note I've used some of my 18650's for well over a year now and haven't noticed any drop off. I am fairly strict on rotation and charging but how long can you use these before you should dump them?