In Azshara, there are swirls called Patch of Elemental Water, where you can fish up such items as Elemental Water, Globe of Water, and Essence of Water. They are mostly located in the Bay of Storms. (See the map, below.)
Around 420 fishing skill is needed to catch other than worthless junk in the open water of Azshara. However, when fishing a pool, this does not matter, as when fishing a pool one will always catch its product.
Coordinates of known poolsEdit
WotLK Patch 3.1.0 (patch date::14-Apr-2009): You can now fish anywhere, regardless of skill. Every catch has the potential for fishing skill gains, but you are likely to catch worthless junk in areas that are too difficult for your skill.
Pilt:WoW Icon 16x16.gif Patch 1.9.0 (patch date::03-Jan-2006): Patch of Elemental Water added