Every time you jump, the force of your weight compresses the fiberglass spring, causing the back foil to change its angle. From the same impact of your jump, the angled back foil is pushed downward to generate the propulsion.

The front foil is locked to a constant height in the water by the skimmer, which planes on the surface of the water.

The image above shows the AquaSkipper during the upward portion of the jump.

The image above shows the AquaSkipper during the downward portion of the jump. The force of the jumping pushes down on the back foil and compresses the spring.