We just finished a Galaxy cruise. I would not drink any water on the ship and believe those that said it's as pure as the bottled Avivon, sold at the bars, ice cold, are kidding themselves. You can bring water and liquor in reasonable quantities back on the ship. If you are coming back with a case of wine the steward will hold it until departure.
Buy what you need on shore. Great bottled water with and without gas is available throughout Europe. Use the ship's bottled water as needed. This will probably be the smallest and best charge on your sea pass. You don't want to shelp a box of water around after a day of touring in summer heat. Benny & Boo