I’m not advocating anyone doing this.  Really. I’m not.  But if you WERE to, say, trim a skateboard to fit the bottom of a whitewater kayak and bolt the whole mess together, put yourself into it, and drop into your local skatepark… then, while I would NOT be fiscally responsible for what happened next, I WOULD be owed some photos.  That’s all I’m saying.

Here you go: You could, (YOU, not me… I’m not, legally or otherwise speaking, saying that ANYONE should try this) bolt these things together and let me know how it goes. And send photos.  Remember it was YOUR idea. Click on ’em if you wanna shop ’em.
Liquidlogic Stomper Whitewater Kayak-Blue-Knight-90
Santa Cruz Land Shark Rasta Skateboard Complete