A boat stabilizer having an upper harness for attachment to a vessel, the upper harness having an assembly control system for controlling attached wing assemblies, each wing assembly having a wing attached to the assembly control system and a wing mount attached to the wing and the assembly control system. The boat stabilizer may be further comprised of a controllable parasail comprising a parasail canopy, a plurality of parasail cords attached the parasail canopy, a parasail mount attached to the upper harness and the parasail cords, a parasail control rudder attached to each parasail cords, and yaw and pitch controllers, both of which are attached to the parasail control rudder. The assembly control system is configured to work in conjunction with the controllable parasail to provide the desired balance of vertical lift and forward propulsion to the attached vessel, while also providing directional control to the attached vessel.

An auxiliary hull unit detachably mounted to a transom on a marine vessel, wherein the hull unit is mounted at least partially below the water line of the vessel and arranged to extend rearwards parallel to the rearward extension of hull sections adjacent to the hull unit. The hull unit comprises a rear hydrofoil system for the marine vessel; the rear hydrofoil system comprising at least one pair of foldable hydrofoils which are pivotable in a lateral direction relative to the hull unit, wherein each hydrofoil is controllable by at least one actuator for displacement of the at least one pair of foldable hydrofoils in the lateral direction of the hull unit between a stowed position and a deployed position. The hull unit can be provided with a propulsion unit.

An auxiliary hull unit is detachably mounted to a transom on a marine vessel. The hull unit is mounted at least partially below the water line of the vessel and arranged to extend rearwards parallel to the rearward extension of hull sections adjacent to the hull unit. The hull unit has a rear hydrofoil system for the marine vessel. The rear hydrofoil system has at least one pair of foldable hydrofoils which are pivotable in a lateral direction relative to the hull unit. Each hydrofoil is controllable by at least one actuator for displacement of the at least one pair of foldable hydrofoils in the lateral direction of the hull unit between a stowed position and a deployed position. The hull unit can be provided with a propulsion unit.