I understand what you are saying. The question is how much energy does it take to pump the air to a given depth for which the combined torque exceeds the amount of energy required to pump the air down there. kinda like a water wheel generator but in reverse. That is a damn good question but I would think it may consume more energy than it produces. Why not just run a straight pipe into the depth of the ocean and let the pressure from below force water out the top and capture that energy?