Efoils are self-propelled all-electric hydrofoil boards. You may not be familiar with the term "hydrofoil", but you probably have seen them. A hydrofoil is literally a wing that is attached to the bottom side of a surfboard (or boat) to create lift underwater. This allows the rider to lift the board above the surface of the water to achieve a flying action which is very exhilarating. An efoil combines the board with the hydrofoil and adds an electric propeller to generate enough thrust to achieve flight.