If you catch the parts of the video where they are actually skimming on the waves and the camera is scrolling across the wave giving you a side view of the skimmer, you will notice they are also "pumping" their boards to stay afloat.
This answer may be a little late, but I found this thread searching skimboard sites on Google. It actually is not making the person faster. Watch and you will see that the person is slowing down. Skimboarding is basically hydroplaning. Skimboards are smaller than surfboards, so they do not have...