Here's another design based around corrugated plastic. Site is a little thin on details, although there have been links from Make and Gizmodo (that second one has a picture of a actual craft).

Our friends a Eli Boat also have a blurb up with a picture of a craft in the water... I think it's the same boat.

Origami boat is a light folding dinghy for sailing fun.

Almost three meters long, Origami boat carries one adult and its extreme lightweight structure makes it exciting to sail. Afterwards it folds up into a flat pack to the same size as a windsurf board and can be easily carried by one person, transported on a car, stowed on a flight or stored in that little space in your garage.

Patent pending.