The McKenna to power plant float on the Nisqually is a fun float. Do that as soon as you get comfortable with the boat. That was my second float in my pontoon boat, and I had no problems and lots of fun. Some nice waves in the rapids, and several neat boulder gardens. It's about 9 miles, I think, and it only takes about 3-4 hours. It may have changed since I did it, but I recall the only significant hazards being a big boulder drop on river right in the first big rapid and a small sweeper (that's probably washed out by now) on river left in the second one.