i have no clue, personally im not so big into water sports so i dont know how these things are done, but im gonna guess and say something like anchored down to the bottom?
not sure what he did, but i just made a really tall rail that would sit on the bottom of the lake anchored down with rocks. that slider looks fun though.
liked the tee. the afterbang definitely looked forced though, but then again it is wakeskating and the tricks were really sick. has potential to be awesome