On our August trip, we saw people asked to remove water shoes when they tapped in to Ohyah and Ohno, and we saw people with footwear on Krakatau Aqua Coaster, and the lifeguards were definitely fine with it. Some kids wore water shoes on slides in the water play areas. If you have to remove water shoes on Ohyah and Ohno, I would imagine you can't wear them on any of the "drop door" body slides. But it might also be inconsistent, in terms of what team members enforce.