A potion of Water always appears as a clear potion. An identified, blessed clear potion is labeled 'Holy Water' and an identified, cursed clear potion is labeled 'Unholy Water'.
Quaffing any potion of water has no effect.
Pouring holy water on an item will bless it, or uncurse it if it is cursed, while unholy water will do the opposite.
Potions of water can cancel fire vortex, dust clouds and fire elementals when thrown at the creatures.
Potions of Water can be created by zapping any potion with a wand of cancellation or as a random result of dipping a potion into a fountain.