Combine a kite, a modified inner tube, a rope, & a boat, and what do you get? Kite tubing (a.k.a. Darwin award winner).
The Wego Kite Tube is an insanely bad idea — it's totally unstable and will flip you right off. This video shows a dude falling from 35 feet at 35 mph. Not surprisingly, it's been recalled due to at least 39 injuries and 2 reported deaths. YouTube has a bunch more videos. This blog entry has lots of comments by people who were injured.