Imagine being stuck inside a plastic ball and being rolled down the hillside.
Thats exactly what zorbing is all about. You get strapped into a giant PVC ball which can be rolled down a slope. Alternatively, I guess you can do a hamster run inside it to get it moving. There is a 2ft air cushion around the inner capsule, which protects you from shocks and keeps the ride safe.
The HydroZorb variant has a bucket of water added to it.
more about it on www.zorb.com