The Challenge mode for this dungeon is unlocked for the weekend (and perhaps longer).

Note that to access this dungeon while Jade Forest is closed, you must speak to the Temple of the Jade Serpent Teleporter NPC, who can be found on the northwestern side of Halfhill, at the center of Valley of the Four Winds.

A few relevant testing notes:

You must have completed the Heroic version of the dungeon once in order to attempt the challenge mode.

Item level will be normalized to 463.

There is no queue system for challenge modes; groups must be formed manually and you must zone in from the outside world.

The current Gold/Silver/Bronze times are not final.

While the challenge is active, the group leader may Reset the dungeon at any time via a drop-down accessible by right-clicking your unit frame.

You may want to dig up those dusty keybindings for things like crowd control and interrupts.

Enemies in Challenge mode dungeons are 1 level higher than in Heroic versions, as a rule, such that bosses are now level 93.

Please use this thread to share feedback regarding the dungeon, including information on group composition and completion times.

The Dungeon Journal only reflects Normal and Heroic abilities, and does not have a separate section for any added mechanics on Challenge mode. Consider that part of the challenge, as it were. :)

In the case of Befouled Waters, you may want to take a look at the buffs visible on the boss during the fight, as well as the combat log tooltip of the effect that is killing you, for a hint.