Eternal Water is not quite as much needed as the other elemental materials, although Blizzard has tried to even out the need for these in Wrath. As always, they can be created using 10 Crystallized Water. (Some might call it “Ice”)
Farming Eternal Water in Zul’Drak
There are two spots to farm Eternal Water in Zul’Drak. One is the Crazed Water Spirit to the south, and the other is a bit further north, the Frozen Earth. Although this one doesn’t look it, it does actually drop water.
Storm Peaks Eternal Water Farming
The Icebound Revenants in the Storm Peaks have quite a good drop rate for Crystallized Water. They can be found just north of K3, as seen in the image below: