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Were you looking for the corpse of the Whale Shark (Thousand Needles) <Whale Shark> in the water of the Thousand Needles?

Whale Sharks are large sharks that roam Vashj'ir and have been rumored to live in the now flooded Thousand Needles.

Notes

Currently, in the beta it can be kited but hits for 500,000+ damage.
It is said that no matter how skilled the group is, if there are not enough players and they draw more than one at a time it will lead to an invariable death. Groups should be wary of the fact that there is more than one whale in Vashj'ir.
Incredibly, there is also a whale shark corpse in the Shimmering Deep of Thousand Needles. It apparently sunk a pirate ship full of treasure. It would seem that the Whale Shark had gotten lost, and swam through the channel connecting the Shimmering Deep and the sea, thus trapping itself.
A Whale Shark's death is required for the Cataclysm achievement From Hell's Heart I Stab at Thee.
As noted in the achievement's description, the Whale Shark drops no loot.
In Thousand Needles there is a Dead Whale Shark bashed in the ground.
This mob, regardless of how far away it is from your location, can be targeted using the command /target Whale Shark. This is useful to many Roleplayers for when they need to be in a combat stance.

In the real world, whale sharks are filter feeders, with a diet mostly of plankton.
The name of the achievement "From Hell's Heart I Stab At Thee" is a line from Herman Melville's Moby Dick. As the Whale Shark drops no loot despite being quite difficult to kill, it is likely that the Whale Shark's inclusion in the game is a reference to Moby Dick.