I second the vote for water shoes. I got inexpensive pairs for everyone at Academy Sports, but I'm sure Walmart would be a great place too. Some members of my family had to get a size bigger than they normally wear because water shoes are on the tight side.
Now that's a deal that I have not seen at Walmart. I found a nice pair of water sandals for half price for myself, and the water shoes for my boys.
We're going to Disney World next month.