This is a cool invention that I would really like to add to my gadgets, since I love water sports and any activity that makes me stay in water.
Flapping wing propulsion devices are hydrofoils that generate propulsion by forcing a foil to move up and down in the water. The forward motion of the foil then generates lift as in other hydrofoils. A common design consists of a large foil at the stern that is used both for propulsion and keeping the passenger above the water, connected to a smaller foil at the bow used for steering and longitudinal stability. Riders operate the vehicle by bouncing up and down on a small platform at the stern, whilst holding onto a steering column. It is started and landed from the shore, or preferably from a dock, and requires a bit of experience. When moving too slowly, it will sink, and the range of possible speeds is 9–30 km/h (5.6–19 mph; 4.9–16 kn)