Rift Achievement:Are You Nuts!  

Walkthrough

Defiants be warned; There are Guardian NPC's all around the relevant area!

The bridge you need to cross to start going up the tree is located at 5244, 3098 in Gloamwood.

Continue up around the tree following the bridge pathway until you get to the top. There will be a small balcony/deck thing at the top of the tree that you can go up and there will be a small storage room. Stand in this doorway and make sure you face out towards the water.

Run as fast as you can (mounted or otherwise) in the direction the door is facing. You should note that you want to land in water, so face Northwest when you do this.

When you hit the water you will earn your achievement!