It was fun. I got to walk under the bridge.
My friend said the jump wasn't very scary. But the photos of the jump taken by the bungy company's cameras are really impressive and look really extreme (I don't have access to those photos right now) . So if you want to have a mild bungy experience and awesome photos, I would recommend this.
Here are some photos I took from under the Harbour bridge:
The company that does this is called AJ Hackett.
More info on their website: http://www.bungy.co.nz/auckland-bridge/auckland-bridge-bungy
