A tug boat 1 tows an inverted hydrofoil 15 at 60m depth in the North Sea with an intermediately positioned cable float 10 added to prevent wave action acting on the tug boat from being transmitted to the hydrofoil. Nutrient carrying seawater is propelled up to the photic zone such that Phytoplankton proliferate, so boosting fish stocks now in decline. The cable float when fully submerged is able to support the downforce applied by the hydrofoil to maintain an obtuse angle between a towing cable 7 connecting the tug boat to the cable float and a main cable 13 connecting the cable float to the hydrofoil. Less than 2 percent of energy yielded as biomass is needed to power the tug. Floating varieties of seaweed that reproduce by vegetative means can be converted to fuels with the crop confined by natural currents so access by shipping is not restricted.
