Abstract: The subject of this invention is a submerged airlift pump using multiple concentric pipes with diameters that increase as they near the water surface. Water initially accelerated into the lowest pipe section is progressively decelerated in subsequent pipe sections, increasing the residence time of the bubbles and hence the total driving force of the pump. Pipe proportions are optimized with gas flows to maximize total pump discharge at extremely low pumping-heads, resulting in ultra-high pumping efficiencies. This device can be used to promote circulation of large volumes of deep pond water, deficient in oxygen, to the surface, creating an increase in the exchange of gases between the atmosphere and water with minimal energy requirements.