The 21-pound Butterfly K-PAK skin-on-frame kayak folds and stows in a backpack. The assembled boat has an LOA of 9 feet, 3 inches and a beam of 30 inches. The aluminum frame remains within the boat when folded and pops open in a few seconds, according to the company. The lower portion of the frame is attached to four independent inflatable tubes that run the length of the boat and fill simultaneously with the provided pump, pressing the frame to the urethane skin. The welded seams are waterproof, and the boat comes with an inflatable seat. $875. Folding Boat Co., Holly Springs, North Carolina, (919) 670-6890.