The third example is one of a propeller and a swimmer alongside with curved lines drawn to show a circular, spinning path of action (see Figure 3). Although it is assumed that this illustration was meant to convey the idea of how forward "lift" can be developed by a lateral movement, it runs the risk of misleading the reader. It is safe to say that a swimmer's arm action in crawl stroke cannot possibly function in the rotational manner of a propeller and any analogy between a swimmer's arm action and a propeller must be treated with skepticism. This analogy also is invalid for swimming.