You become one with the rest of the molecules floating around. ESSENTIALLY, that is god. We are all very tiny pieces of an eternally omnipresent being. Not like a spaghetti monster, more like atomic structures and the electricity that run through them. I don't believe that there isn't something deeper there, but it's not God in the traditional sense that people want to believe in.

If you think about it, quite a bit of the water you use is probably recycled from human bodies. We are all made up of naturally occurring elements that are found in nature. It only makes sense that it is returned from where it came. Your body mass is basically overtaken by insects and fungi, dispersing you back into the earth. To be recycled again and again.

Quantifying the "soul" is difficult though, I would say that the brain acts as a conduit for molecules to observe and interact with eachother on a more refined level than their basic structures allowed. They probably got bored of floating around and started messing around, and voila, stuff happened on earth.

In a roundabout way.