We are building an inground pool with rock waterfall. We have been told it would be best not to have the rocks IN water. Instead the rocks will set on concrete "shelf" above the waterline. We also were told that we had to go with chlorine instead of salt water as the salt could corrode the rocks. Any input on these suggestions? We like the look of the rocks slightly submerged giving the edge of the pool a more natural look but if this is less structurally sound will stay with the elevated ledge approach. We are in Oklahoma and the pool actually will be very structurally sound as they hit sandstone and althogh this made excavation more difficult, will provide a great stable base for the pool!