Ori Levin designed a full sized canoe that's completely collapsable and can be stored in a bag that's only 5 x 9 x 28 inches big. Basically, you can have a boat in your backpack.
Called the Adhoc Canoe, it only weighs 9 pounds and takes 5 minutes to assemble. The frame of the canoe is made with carbon fiber and the hull is made of aramid (a synthetic fabric used in racing sails). The boat comes together in a "double wishbone-like structure" formed using telescopic poles. Probably not comfy but certainly clever. Sadly, Levin has no plans to bring the Adhoc Canoe to the mass market.