Not necessarily. I’ll invoke artist’s imperfections here: the precise thing we see wouldn’t quite work, but if Artie takes one step down the cliff and then pulls himself downward by that foot, he can apply a nearly an entire horizontal-leap worth of speed to his initial vertical velocity. And he wouldn’t then have to worry about trying to intersect the cliff face a second time on the way down.

I mean, I’m pretty sure this is the point where he died in that future. All the same events happen, Helen is knocked off and Artie dives to save her. He… sort of succeeds, but hitting concrete instead of water, even exploiting his transformation isn’t enough to survive (and Helen is left in a mostly-dead body).

(Mind you, the whole “water at speed is hard as concrete” thing is literal, there’s really no difference in the first instant of collision. For the water to make a difference, Artie must have done some very precise clever transformation shenanigans at the last second, so that the initial impact that broke water tension was largely taken by a body in the process of ceasing to exist.)

Unless the future gets changed, of course….