Sorry to disabuse folks, but all pools on cruise ships use chlorine (or bromine) to sanitize the water.   Salt water pools:  The chlorine generating systems for land salt water pools are not accepted as being precise enough for use on cruise ships.  If a ship with salt water pools is going to be at sea for more than a couple of days, they will simply pump filtered sea water into the pool continuously, and the overflow flows back to sea.  The problem is that when the ship is within 12 m