Canoe tripping run (20 miles, at only 3 FPM average gradient). It may be possible to shorten the run a bit using alternate accesses.
"Grand Rapids" (at Lat/Lng 46.7640, -89.2717) is the whitewater highlight of the run.
USGS aerial image resolution on Google is quite good. Go to the 'Map' tab, click 'USGS Aerial', and double-click near (not 'on') any of the markers on the river (put-in, take-out, or Grand Rapids), then zoom in to maximum resolution, and do a 'virtual walk' of the river.