My imaginary world

My participation to "The World inside your mind contest" on DA.
What If we all lived underwater, our ground was a water surface and under our feet is endless space? Does it sound unreal? But it is possible! Planet could be a water ball, and people would walk inside the planet, not on its surface. Center of the planet - rocks and caves. And outside the planet is cosmos, full of other fantastic planets.
Probably physicists are horrified with my "knowledge", but I'm an artist after all...right? Ok, it's an awful excuse. But anyway...
Drawing from imagination.