I have seen it done - for a very short time and totally unsuccessfully - on Vance Creek, trib to the Skok. One of our stream surveying crew thought he could save a bit of time and cover more water if he didn't have to walk all the way, so he put in the float tube and had at it. He got to the first riffle, hit the bottom, flipped over, and got soaked. This on a day with snow on the ground. End of experiment. :p