While Whimsicott, Haxorus, and Volcarona resist Water, you probably don't want to surf into them too often. Scald is consistent and won't hurt your partner. Don't Muddy Water. Just don't. It will fail you when you need it. Your 6th slot really depends on what you're trying to do, what your type weaknesses are, and what teams/pokemon you have trouble dealing with. We'd need more info.