Been thinking more and more about doing this. Found a bunch more plans for doing so below:
One Sheet Jon Boat (rowboat like) http://www.instructables.com/id/One-sheet-Jonboat/
One Sheet canoe like boat (Lots of work thought) http://www.instructables.com/id/Building-a-One-sheet-boat-Alternate-Building/
Another canoe like one here http://www.instructables.com/id/Building-a-One-sheet-boat/
Making a plywood kayak (WAY TOO MUCH WORK) http://www.instructables.com/id/Making-a-Plywood-Kayak/
More rowboat like (easier than the canoe/kayaks). http://www.instructables.com/id/Construction-of-Two-Portuguese-Style-Dinghies-Sma/