I've never experienced the "water problem" but wouldn't it probably only cause one slide to stick? I'm sure both could stick at the same time but it's unlikely and surely won't happen everytime.
If both slides are sticking at the same time it's probably your cable but could also be your throttle housing if you've gotten anything stuck in there. A temporary fix would be to lube your cable, but you might want to replace it. My throttle used to stick sometimes and changing the cable did the trick.
If only one slide is sticking it could still be the cable but is more than likely something in that carb. Specifically somewhere with the TORS assembly or slide.
If you can't tell whether it's both or one carb clean both carbs real well, then possibly replace cable.
I hope I've helped. It's really late and I'm tired.