My advice is RENT A LOCKER! I have been to Disney a zillion times and the water parks a half a zillion times. In my mind, Disney is a magical place where there is o crime and is no evil. Plus, I rationalized, who would pay that much money to get into a park to steal.
Well, it turns out that it is a pretty profitable endeavor. I had hidden my camera and smart phone deep in my bag and left it on a chair. When I returned later, the bag was gone - later located, sans belongings, in a men's room trash can. Before I left for the day, we discovered at least five other victims, one of whom was taken for $600 cash.
I was sad that someone stole my camera and phone but they were replaceable. What hurts is that someone stole my magic
Don't be cheap / lazy - get a locker.