Where do cruise ships get fresh water?

How do cruise liners get, and keep, fresh water on board – eg for drinking?

Cruise ships are of course, surrounded by water, but it needs to be made suitable for use by the passengers, so all ships have desalination systems on-board, which remove salt and impurities and turn it into fresh water. This water is suitable for washing and cleaning but there is another process to make it suitable for drinking, called mineralization, which restores minerals which were removed during the desalination process. This fresh water is stored in massive on-board tanks, which typically hold up to 500,000 gallons. After the water has been used by passengers, it must be treated again before it can be safely discharged into the ocean.