The Steam Lift Pump of the Ocean Thermal Gradient Hydraulic Plant is patterned after the well-known but apparently not well understood air lift pump, which is an effective but inefficient device for increasing the head on pumped liquid, usually water. Instead of pumping compressed air, an expensive and largely unsuitable gas into the bottom of the pump tube, a partial vacuum is applied to the Steam Lift Pump, at an absolute pressure just below the saturation pressure of the pumped liquid. Cavitation bubbles grow from nuclei formed by degassing the incoming liquid in a cavitating venturi of special design. The low density foam formed by the steam bubbles is pumped to a maximum theoretical height (head) about 4 times the sum of the pressure head of the immersion of the pump tube in the liquid and the head of water supported by the vacuum. The bubbles are broken, their steam content condensed and the resulting dense water flows through an hydraulic turbine.