weird watersports

We met these South African family at the Inhaca beach.. and the two guys were trying to get this weird water'hopping bike thingie to work. Basicly you get pushed off the pier and you step on this thing, you start pumping with your legs up and down , and if you do it properly the thingsie hops on the surface of the water , it has large water wings underneath which aparently do the job. Needless to say I couldn't go more than a few meters and I tried hard.. The guys were doing much better, they could go for up to a 100 m.. quite impressive.. quite weird too, well I guess I should learn how to do it some day..