A collapsible vessel (10) reconfigurable between expanded and collapsed configurations. A sleeve combination (12) has an inner sleeve (16) rotatable relative to an outer sleeve (14). A liner (18) is retained by the sleeve combination (12). The sleeves (14, 16) have opposed major walls (44, 46, 52, 54) divided by opposed fold line formations (45, 49, 53, 57). Arrays of flexion apertures (66, 68) span a lateral range from adjacent to the respective fold line formation (45, 49, 53, 57) toward a central portion of the major wall (44, 46, 52, 54), and an aperture density can vary generally based ondistance from the fold line formation (45, 49, 53, 57) to promote a true-round confirmation of the expanded vessel (10). A lid structure (28) with a disk (30) and opposed retaining tabs (36) can be selectively engaged with the liner (18), and a retaining strap (20) can be pivotally coupled to the sleeve combination (12) with a first orientation encircling the sleeve combination (12) and a second,longitudinal orientation. A storage bag (70) with first and second longitudinally-disposed stays (82, 84) can receive and further compress the vessel (10).