You guys beat me to it! I was thinking of the airboat idea last night and I was planning to post about my idea today! ok, well, I'm guessing you guys still want to hear it. I would take a foam block and shave it into the shape of a J16 Carolina Skiff (just the hull) with a filled hull (totally flat on the top and bottom)-because I think it would float and work better that way. Also, since I live on a canal, which is saltwater, and would be mostly using it In saltwater, I would fiberglass the hull since I already have a fiberglassing kit. I will design and build the hull first if I plan to then possibly get my second AA and work out an idea for the electronics.

I have one question about the actual plane, what are the three aluminum strips for?

edit: I forgot to mention, It would be nearly impossible and I'm not gonna try it, even though it would be so awesome, a micro hydro foam using the kit, for anyone that doesn't know what a hydro foam is, here is one including a couple of videos.
http://www.hobby4less.com/hydro_flyer.htm