If the girl is getting paid by the club for selling water, then at $2.35 a bottle they should be making enough profit to pay her properly. If she is buying in the water herself and selling it with the permission of the club, again she is making enough profit already.
Caddys working for tips alone are a different kettle of fish, and if i am ever in the right job where i can afford to play these country club type courses, and they have caddy service then obviously, you need to be paying these guys wages yourself ... $15 dollars an hour seems fair to me .... more if they are good and you can afford it!
As a European the one thing we hate about going to the US is this automatic tipping rubbish .... employers should be paying people the correct wage, and we should not have to make up the difference!
As for the guys that wash your clubs etc. (I find this hilarious by the way).... if you want your clubs cleaned by them, you pay up ... if you dont you dont! Just like the guys working in bathrooms in bars in Dublin, I'd rather wash and dry my own hands thanks, and i certainly aint gonna feel guilty for not tipping them. Not when I'm paying €5 a pint.
At the end of the day you guys are paying a hell of a lot of money to play these type of places, and any additional services should either be paid by the club, or the customer, but not both!