Could use a little more information. How does it float? Is the cloud attached to his shell? Is the shell/body made of lightweight materials too?
The cloud top hat is very significant. If it trys to jump, thre cloud top hat pulls it up. If that makes sense.
Well, it practically could be another animal under there.. And I fogot to mention, but the turtle can be subject to color change, it doesn't have to be that ugly green.