Perpetual Motion Machine?

Allow me to clarify the design: the right half is filled with water, while the left half is filled with air. This is a side view of the system. Water lifts the buoyant object up on the right, and then drops it back down on the left. It is then picked up again by the water and the cycle perpetuates.

Aaaaah, makes more sense now; I was thinking something similar but not quite that.
I guess only issue would be preventing water from spilling into the other side yes? Otherwise it sounds like it would work just fine.