We did Busch Gardens twice, Seaworld Twice, MK twice, AKL once and TL once in 11 days. We tend to spend all day in a park once we are there - so alot of walking each time.
I got my kid's sports sandals from Wallmart for under $20 a pair. My husband and I picked ours up from Zellers for about $25 a pair.
We wore nothing but those sandals the whole time we were in Florida. Packed sneakers and socks but all they did was take up space in the suitcase. I saw people with sneakers and socks - that looks so hot! And what about water rides - ugh. I bet they had soggy toes after some of those.
So I'd recommend stopping by Wallmart (or Zellers if you are in Canada) and finding a comfy pair of cheap old sports sandals that fit your feet properly (we tried alot of pairs before we found ones that suited us). They should do you just fine. We didn't have any problems at all with our cheapys - and they are still in perfectly good shape. And our feet are too.
The only feet problems we had were on the kids. After a day at the beach in soggy water shoes, their feet had some pressure point sores. Nothing worse for feet than being soggy. Amazingly, their cheap sandals were still comfortable, even with those sores. Can't beat that! We forgot about the water shoes after that, and just used the sandals on the beach, at the pool, in the waterpark. All our sandals dried off quickly anyway.