My 12 yo got this for Christmas:
http://www.boatworld.co.uk/Sportsstuff%20Gyro
and today was the first time out.
The video's are in HD, so maybe watch them on Youtube and select 720 or 1080.
It's designed to roll over and over with the rider hanging on for dear life - hence the nickname "Vomit Comet". It has a stainless pivot on the front of it. From a boat drivers point of view, it's not as dangerous to tow as it looks, it actually spins out a lot less than a tube - it has a nice rolling action as it goes over the wake.
I gather from Internet reviews that it depends on the weight of the rider. The heavier the rider, the more it rolls. But the rider also has some control and can lean inside it.
Inside, it has 4 grab handles, so you can hold on to any you can managed to grasp! Talking of inside, here is a shot of inside using a cheap Chinese GoPro copy:
Anyway, it was a blast. He got out and said "Best Christmas present ever!"
I'm yet to have a go....
Nick