Charge Water Orb is an enchantment spell that requires a Magic level of 56 to cast. It can only be used on the Obelisk of Water, located on an island in Catherby bay, accessed by climbing a ladder in Taverley Dungeon very close to the fire obelisk. Each cast will turn an unpowered orb in the player's inventory into a water orb.
Using a water orb on a battlestaff makes a water battlestaff. This requires 54 Crafting and gives 100 Crafting experience.
The fastest method of charging would be to have a Player-owned house located in Taverley, with a mounted amulet of glory, requiring 47 Construction, and using a Teleport to House tablet to get to Edgeville via the mounted glory, bank, and then return, requiring two tablets per trip. It is highly recommended to have the high agility requirements for the two obstacles as it significantly lessens the time for each run and makes this a good way to make profit.