A hydrofoil (or foil) board is a water board with a set of wings underneath it. Like an airplane, those wings lift the board off the water when a little speed is added. However, instead of flying on air the hydrofoil flies on water. The power of the eFoil electric hydrofoil surfboard is controlled by a wireless hand controller and has a top speed of 22 knots (25 mph). I bet it's a pretty exciting ride at that speed. It is battery driven, the battery lasts about an hour. Cost is presently $12,000.
I found two videos: the first one shows it in action on lakes, rivers and oceans and the second explains how it works and the mechanism that drives it, explained by the developer. Click on images below for videos.
What drives the Surfboard (hydrofoil)
(sorry about the obvious distraction, it's the best image I could find)