Have you run the Salt? If not, you should be aware that there are several sections, not just the Maze, that are continuous Class II/III. In a ducky you will be working most of the time until you get below Jumpoff Canyon. Black Rock and Quartzite are portageable at low water, but the Maze and Corkscrew are not.
Of course, swimming isn't necessarily bad with good safety set up.
"There is NOTHING--absolute nothing--half so much worth doing as simply messing about in boats. Look here! If you've really nothing else on hand this morning, supposing we drop down the river together, and have a long day of it?" -Wind in the Willows