Sentence:  The water in Thor 's big swimming pool had been covered with a blanket of thick , foamy soapsuds - fashioned , of course , from ZING - Joyce had dived from the board into the pool , then swirled and cavorted in her luxurious `` bath '' while cameras <WSD>rolled</WSD> . 
Meaning of the word marked with <WSD> tags:  begin operating or running