I want one.

http://www.wimp.com/waterinvention/

That. Looks. Knackering!

Look a bit like a twit bouncing along, although i like the idea.

Haven't these been around for a few years now?

why can it only be used in Cool water?

It's definitely been around for some years, but I believe the spring at the front is new-ish.

Won't get me on top of one of those.

Well not for more than 3 seconds anyway

They look easy, but every person i have seen attempting it first time takes a bath.

Thing is, you want to sell this thing, right? So you advertise it with a well-wrapped-up bloke on a cold-looking lake with the sun not shining.

Spot the deliberate mistake!

Surely, the way to power this thing is not to have the operator bouncing up and down, but to have the operator pedalling, which in turn, rotates a flywheel, with a large off-centre weight (in other words, something to make the up/down movement)

In part of the video, the rider is putting some serious effort in - I doubt it could be kept up for very long

Its also flawed - you HAVE to keep bouncing, otherwise you sink - most other water craft float if there's no motive effort

I like you'r idea Nigel. But for a short bit of fun with friend's taking turn's,it could be a hoot!

Buy one joe...gota be a lake near spa....

I think this would add too much weight; you'd have the weight of the pedal/drive system, seat and support structure plus a s pretty hefty weight to create that level of vertical movement. Say, (a wild guess) an extra 50kg.

Just don't get tired in the middle of a lake...