One thought, in TPM, if Qui-Gon really got mad at Obi-Wan for getting his saber wet, that could only be a temporary issue because they then went and jumped in a lake. So, unless they have little ziploc bags with them they got their sabers wet, then promptly used them a few hours later to save the queen.
So water likely won't destroy a lightsaber then, at most it would just dissable it till it's dry, kind of like a zippo.