sentences:  The most popular propulsion systems involve a kayak paddle that breaks down into two to five pieces.Most often they are paddled from a sitting position, although kneeling can be advantageous in some situations.Pioneering use of packrafts is difficult to trace, as float tubes, inner tubes, and other small boats can in some of their uses be considered equivalent to packrafts, and have been used around the world for over a century, beginning with the Halkett boat.