Two layers of 4 mil plastic liner. Two threaded PVC fittings. 140 gallons of rainwater.
You could fill it up and jump on it, but we recommend using it inside a bench like this (plans available in the 140gal DIY kit).
btw Scott is 190 lbs (ok 200+ after Thanksgiving). Really, please don’t jump on the liners. This was just for testing purposes…
(but it was pretty fun)