Sorry bear with my ignorance.
I was just asking of there would be a difference in energy expenditure in lifting an object through air against gravity vs forcefully inserting that same object (bouyant) into the bottom of a column of water and somehow mechanically recapturing some lost energy...
Sorry, just to clarify the setup, the object would be outside (not in) the water column and would be forcefully inserted at the very bottom of the water column.
So the question is the amount of force needed to insert the object into the column compared to the energy produced by the bouyant...