A foldable seat or support structured from one or more blanks made of a lightweight and waterproof material which are tightly secured together at their ends and are cut and scored to provide fold lines and integral and foldable panels which can easily and quickly be folded into an assembled and operable seat or support capable of supporting heavy loads and capable of being used repeatedly even after being exposed to moisture. The seat is also structured to permit certain panels of the assembled and operable seat to be unfolded and thereafter refolded in a certain manner or sequence for a quick conversion into a tightly secured and self contained compact bundle or package for carrying, for use as a seat cushion, or for storage. A shoulder strap can be attached to the tightly secured bundle for ease of carrying or storage.