Hahaha. Penis rocket. Friggin' awesome!
Since the fish form is not constrained to fall straight down when in the air, and behaves more like a Newtonian projectile, you can launch off from your penis rocket just before it wilts. The übervine hurts fish form, and sends you caroming off in the opposite direction.
V. fun. See that nice parabola on the map there? Like that.

And, Cryzbl you son-of-a-gun. Now I need to go hone my vine-wall-jumping skills to get up there, since they are currently nil. Well done, though!
Alec, is there maybe an easier way to get up there than how Cryzbl did it? A hidden rock in that section, perhaps, or something else we haven't tried?