Heavy duty dry bags - moving your boat

For the longest time I have carried one of those heavy duty dry bags as a spare bag.  I am constantly questioning myself on why I continue to carry this beast of a bag.  It does not fold down small when empty and when full it is difficult to stow.  However, the other day, contemplating how to get my boat up the shear ledge rocks of an Island, I thought, wow, I can use the bag as a roller.  It was like one of those great epiphanies that just reaches up and hits us on the head.

Well, low and behold, it worked spectacularly.  I had some clothes in the bag and added a little air, and it made a perfect roller for the boat.  I simply placed it under the bow, and pushed the boat a bit and then switched to the stern and pulled a bit.  It kept the boat off the rocks and I was able to work the boat up a very steep rock ledge without causing any wear and tear to the bottom.

Needless to say, I will now keep that obnoxious bag with me for the foreseeable future to help in moving the boat up the rocky shores of Maine and Canada.