RCCL is in the process of converting their pools from saltwater to freshwater. On our November Enchantment cruise they had one freshwater pool but I don't quite think they had all the kinks worked out since the water looked a bit murky and green.
Reminds me of the old joke about cruise line pools: The lady asks the crew member "Are the pools salt water or fresh water"? The crew member says, "They are salt water, ma'am". The lady says, "Oh, so that's why the water is so rough".