Perpetual Motion Machine?

I went to the perpetual motion Wikipedia page and found this:

The "Float Belt". The yellow blocks indicate floaters. It was thought that the floaters would rise through the liquid and turn the belt. However pushing the floaters into the water at the bottom takes as much energy as the floating generates, and some energy is dissipated.

Picture:
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Seems very similar to my idea. I guess the area that makes this impossible is the transfer from air as a medium back to water at the gate.