In reply to BigBrother:
Yep.
Chalk + water = ruined chalk
There are ways of dealing with it though.
One way is to not take a chalk bag and chalk up heavily on your forearms so you have something to dab mid- ascent.
Another and better option we have come up with here is the duct tape chalk bag.
They're not hard to make, they're water resistant- so you can dry them off quickly with a towel- and they're cheap as chips.
One roll of duct tape costs a few quid and all you need above that is something to stiffen the opening (a loop of plastic tubing from your local DIY shop) and some string/ cord to hang it off you.
You can make about 5 or more chalkbags from one decent roll of duct tape.