Check out the Hobie MirageDrive. Anyone use one of these things yet?
Most interested in comments from users

You're not necessarily using a paddle so there could be some stability
problems -- you can't brace. I know one person who has one and it works
very well for him. On shallow stretches of water the fins fold back and he
has to allow inertia to get him across some things.
Also, this person has only one arm, so this is about the only way for
him to enjoy paddling -- and he does very well, thank you...

Joe P.