pool noodles. the hollow kind. split enough to squeeze a shoe in. duct tape shut. put grippy stuff on the bottom if you want.
DO NOT USE ANYTHING RIGID. you wont be able to bounce.
whoever said PVC that is a no go.
"I look at it like this; the park is like a canvas, you practice the art, but being out on a real mountain is like experiencing the painting. I want to get out there. Explore." -Parker White