This wouldn't work for many reasons.
1. Although the valve at the bottom of the water tank would keep water inside, it would require more force to pass through than the balloon could exert.
2. If the balloons are light enough (filled with air) to rise through the water, they wouldn't necessarily float down the other side in order to enter the water chamber again.
Bottom line: it's a pitiful attempt at a perpetual motion machine to provide energy, and it wouldn't work, but it's troll physics. So don't take it seriously.