At the Engineer's seminar on day 4 of our wonder trip, the ship's engineers told us the ship takes on water at the terminal. This water is a 2 and a half day supply. Then sea water is flash boiled and condensed to replenish it. So, at first you are drinking port canaveral water and then as time goes on you are drinking sea water. They are required to chlorinate it to meet US guidelines.
We though the water was just fine for drinking.