Abstract: A collapsible container that can be used as a swimming pool is provided that can change from a collapsed to an expanded configuration. The swimming pool is constructed of a foldable, durable material, and is shaped by way of tension provided by a base spring, which is a coilable spring constructed from a wire having an oblong cross-section. The wire maintains tension when fully extended, but can be coiled or folded upon itself, allowing the base of the swimming pool, along with the rest of the pool material, to be folded and stored in a compact form. Various support spring configurations are provided to automatically expand the pool to full size upon unfolding it from its collapsed configuration. A flotation device may be provided at the top of the side wall of the pool, which floats on the water used to fill the pool, thereby raising the side wall of the pool as the water level rises.