So one of the things I wanted to try on our Grand Canyon trip was to see if using a drift sock like I use in the ocean to counter wind conditions not favorable to fishing or for emergencies where the boat loses power would work for strong UP canyon winds. The genesis of the Grand Canyon Drift Sock Experiment was that we had been warned that the Spring season would have some days where unfavorable winds could really halt any significant downstream progress so I purchased this (amazon.com/gp/product/B0027ABILQ) drift anchor and we experimented with different rope settings off the bow of our 18' raft. The sweet spot was at about 15 feet of rope between us and the anchor. Other important considerations including watching for eddies that could suck the anchor and us off course or whirlpools that could suck us down. Needless to say, it is wise to have a rescue knife handy or some other quick release that would work under tension in case of a snag. The bottom line was that the experiment was a great success. Dave and I were able to maintain a nice steady downstream progress with almost zero effort. A strong rower working at a high level of effort could definitely beat us, but they would be a lot more tired at the end. If I were a future trip leader, every one of my boats would have one of these.