Does 'It is not possible to walk up through the water as at Dunn's River, but steps have been erected at the side of the water to take you to a platform at the foot of the first cascade.' provide a contradiction to the established premise 'Just as at Dunn's River, you can wade up through the water to the platform.'
It is not possible to walk up through the water as at Dunn's River, but steps have been erected at the side of the water to take you to a platform at the foot of the first cascade.###Just as at Dunn's River, you can wade up through the water to the platform.