From the behavior, i am guessing it is a female laying eggs some 2-3 feet up cattail stalk.

According to Washington State Odonata expert Dennis Paulson, writing to me on 12 September 2008:

That's a Paddle-tailed Darner. Lance-tipped (not known from the Olympic Peninsula) would have irregular thoracic stripes. Shadow would have blue spots under the abdominal segments. Neither of these would have a dark line across the face. The only other possibility is Variable, and it usually has narrower thoracic stripes, often no trace of the stripes on the front of the thorax. Paddle-tailed is by far the most common species at this time of year.