A motor driven tug boat tows an inverted hydrofoil 17 at a depth of 60 metres in the North Sea to bring up nutrient rich seawater to the photic zone at the surface. The hydrofoil is towed by means of a cable 19 that may be deployed from a winding drum 18. Phytoplankton proliferate at the surface boosting fish stocks and cultivating floating varieties of seaweed that reproduce by vegetative means. When converted to fuels like natural gas only about 5% of the extracted energy needs to be re-invested for operating the system. The result is to provide a source of sustainable alternative energy that also reduces acidification of the ocean and provides a means for sucking carbon dioxide back from the air.