Its good there was a sign like the one pictured above, but I would think fast running powerful water below me, leading to a shoot, leading to and going over a giant cliff should kinda make a point all its own. "All it would take is one slip" (the brain should say to itself, in *any* language) "and whee...last super slide ever".
There is actually an analogous kill-zone that unfortunately does the same kind of business (though fortunately not as much) in Sequoia NP. From below and from a distance it looks very Rivendell-esque, kinda like a several mile long 45 degree incline coming like a narrow ribbon out of the high sierra peaks in the distance. Up close it is not nearly so smooth. Added to the 45 degree angle of the "slide" itself there is a kind of V with glacially polished granite up to a hundred yards or so on either side. It all looks so mild and peaceful, and in spite of the signs every year people get captivated, wander too close to the V, slip and slide down into the sluice, and find out the hard way it isn't like a smooth water slide at all up close. There are always a few each year that die, in spite of the fact it has been going on since forever, apparently.