Hi Denise,
Thank you so much for visiting the Disney Parks Moms Panel with your question.
There are some great water rides at Walt Disney World. Two of my favorites are
Splash Mountain at Magic Kingdom and
Kali River Rapids at Disney's Animal Kingdom. On both of these rides, you might get a little bit wet, or you might get very wet!
There are a few factors for my family in how we deal with getting wet while at a theme park. First off, if it is a very hot time of year, sometimes riding one of these attractions mid-day provides much-needed relief from the heat. An early afternoon soaking on Splash Mountain can feel really good for the next couple of hours on a hot July afternoon! In the cooler months, we tend to save these attractions for the end of the day. If we know we want to ride one, we save it for last, and then head back to our resort to dry off and change clothes after that one last ride.
I agree that carrying extra shoes and clothes for everyone gets very bulky. Like you, I carry a backpack to the theme park. On days when I know that we will be riding attractions on which we might get wet, I carry extra socks for everyone in our traveling party, as well as a couple of hand towels and handkerchiefs. I put all of these in a plastic zip-top bag in my backpack. This keeps them nice and dry while you are on the attraction. It is amazing how much work a hand towel can do toward getting you dry, and dry socks make soggy toes feel much better. The handkerchiefs are useful for drying off wet glasses. Then, anything that is wet goes back into the plastic zip-top bag, thereby keeping the rest of my backpack dry.
Please do let us know if you have any further questions, Denise!