Patches of Elemental Water and Pure Water

Both these pools look like bright blue swirling masses of gas, but may be fished just like other pools.
In Azshara, pools called "Patch of Elemental Water" may be found. From the pools you can catch:
For more information about fishing these pools, please read the Fishing Elemental Water topic.
In Nagrand pools called "Pure Water" can be found. These mostly contain Mote of Water. For more information, see the Fishing Pure Water topic.
Muddy Churning Waters (Zul'Gurub)
Most of the waters in Zul'Gurub contain similar sorts of fish to the hot springs of Winterspring. In the waters around the centre island, you will find pools of "Muddy Churning Water". From these you can fish Zulian Mudskunk. Each pools contains 2-4 fish. The pools are surrounded by packs of nasty looking crocodiles.
The only reason to fish these pools is to summon Gahz'ranka. You will also need a Mudskunk Lure, which can be obtained from Nat Pagle after completing the quest "Nat's Measuring Tape". For further details read the quests chapter.
Tome of Polymorph: Turtle can sometimes be recovered from Gahz'ranka's corpse. See the Valuable Fish chapter for details.
School of Tastyfish

School of Tastyfish only appear for 2 hours during the Stranglethorn Fishing Extravaganza. This is held each Sunday, from 14:00 to 16:00. These pools replace all other pools in Stranglethorn Vale.
As the name suggests, School of Tastyfish primarily contain Speckled Tastyfish. Other fish may be caught, including:
For full details, read the Stranglethorn Fishing Extravaganza chapter.
Strange Pool (Serpentshrine Cavern)
In the Serpentshrine Cavern (within Coilfang Reservoir in Zangarmarsh) is a large patch of blue glowing water called a "Strange Pool". This pool contains the same fish as School of Greater Sagefish in the Alterac Mountains and Stranglethorn Vale - Raw Greater Sagefish and some Iron Bound Trunk. After fishing for a period (up to 20 minutes, but quicker with more people fishing), a rare "fish" will be summoned: The Lurker Below. This is one of the dungeon's bosses.
Pool of Peacebloom
When flying between Stormwind City and Ironforge, you may briefly notice a single pool in the elevated lake north of Northshire Valley. The pool is simply called "School of Fish". Empello has managed to fish from this pool, and writes:
"The first catch was 3 Peacebloom and the second catch was 3 Peacebloom. After about 20 catches I had about 60 Peacebloom (varied from 1-4 per catch)."
((Note it seems very likely that this is a bug, and not intended. While Peacebloom is not especially rare or valuable, fishing from this pool may yet be deemed by Blizzard as an exploit.))
Red Snapper

"School of Red Snapper" (illustrated right) can be found in Ammen Ford, Azuremyst Isle. These pools cannot be fished like other pools. They can only be "fished" with the quest "Red Snapper - Very Tasty!" - and that quest requires you to use the Draenei Fishing Net (provided by the quest), not a fishing pole.
Learn More
- Fishing Elemental Water - How to fish Patches of Elemental Water, found in Azshara.
- Fishing Pure Water - How to fish pools of Pure Water in Nagrand for Mote of Water, which combine to make Primal Water (The Burning Crusade only).
- Stranglethorn Fishing Extravaganza - This chapter describes a contest based around pools of Tastyfish.
- Thalen's WoW Guide - Elemental Fishing Pools - Details of Azshara pools, including a map of unconfirmed locations and pictures of the curious Swirling Maelstrom.
- Also in the Pools and Wreckage chapter: Pool Fishing, Locations, Spawning, and Strategies.