You might have heard of this or even been there, especially if you’re Alliance cause it’s in Darkshore.
I did not find this place by myself, but I think I could have. Cause few days after Cataclysm release I was flying around the world exploring, I jumped into a similar maelstrom in Stranglethorn and I died, so I learned not to jump into them.
But this you actually should jump into and you won’t die. Instead it will take you down to a hidden cave beneath the water somewhere, it’s called Bashal’Aran Collapse. There is a friendly night elf there who says she wasn’t expecting anyone down there and is wondering if I’m there to keep her company or just looking for a way out.
It looks like the support and original entrance to the place collapsed. There is a night elf ghost called Telarius Voidstrider. For Alliance he will drop the quest item Writings of the Dark Herald which contains secrets on the path to becoming a Demon Hunter. This quest will give you the achievement Ghosts in the Dark.
You can also read about this place and others here where Ironyca has written a post about different secrets in Cataclysm.