i have a vast imagination so in my mind, there are a thousand and one ways he could have survived.
but one main one pops up. the cavefish have like this whole world in the caves. well what if the caves have openings out on the side of the gorge, i don't know why they would, but maybe they do, maybe a quick escape or whatever. well on his way down Ripburger is caught by a kindly cavefish (kindly in a very small way, lets not tarnish their muderous image). of couse some of you would say that that cavefish would be pulled down as well, but there is a chance they could survive that. i mean think about it, Rip being caught wouls certainly slow him down a little and it may be closer to the bottom by that time so an impact on water may not kill him. think about it.