Alternate spelling of waterboarding. There are several variations on the technique, but it generally involves holding a subject's head in a declined position and forcing water into their airway, thus inducing a feeling of terror as the body believes it is drowning. If performed correctly, water boarding does not leave marks and is not lethal.
When someone falls down and in an effort to "walk it off" and look like they didn't get hurt, they can only "crawl it off" because they have knocked the wind out of themselves..
Did you guys see Marty fall in the turn racing his dirt bike? He water melon crawled back across the track and almost got ran over.