My DD 5,3,1 wear KEENS anytime we go to the beach, water park, theme park etc. They protect their feet and toes, have great traction, and are waterproof. Plus they make each kid about and inch taller for rides/water slides. They are pricey, but Ive seen knock offs for less at Carters. Crocs give my girls blisters for some reason, but I'd view those as a reasonable alternative to true water shoes. We also use Natives which are croc material, but shaped more like a converse so they stay on better and seem better developmentally for young walkers
Wouldn't hurt to bring Water Shoes. My family and I do this. Just an FYI, they will NOT be allowed to wear them on Pelican's Plunge (water slide area) at Castaway Cay.
I second the comment about the hot deck, but I thought it was worse surrounding the pools (some of the Aqua Duck line is in the shade). We didn't have water shoes for the Fantasy Eastern Caribbean in July and they're at the top of the packing list for our cruise next year.
And Castaway isn't always nice soft sand. Our first time, in early 2013, there was a few months after a big storm, and the "sand" was downright painful. We had to buy expensive Disney water shoes for hubby and son (who had refused to go in on the Budget Board deal on water shoes through Land's End) on the island!
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