temperature. Obviously in Florida it only gets so "cool", but think about DHS... it's a concrete wasteland and the heat just absorbs and has nowhere to go but sit there. It's sort of the same at DAK, even though there's a nice river, the dense amount of trees traps the heat in, which is why many claim DAK to be the hottest park.
Also, name me one great park in the world that doesn't have some sort of waterway.