A few years back, French jet ski champion Franky Zapata developed the Flyboard, this let you follow behind a speedboat while attached to a set of water-power rocket boots. It was a great invention but it seemed rather clunky and weighty.
However Zapata is back with the Hoverboard which does the same thing, but attached to a surfboard with a single nozzle coming out the back of it. This gives the Hoverboard the ability to be able to perform trcks and stunts on the water, which you wouldn't have been able to do on the Flyboard.
Downsides? You're going to need $6000 for the Hoverboard and access to a speedboat.