Nanotechnology start-up Ecology Coatings says it has developed a spray-on coating that, when properly dried, waterproofs materials--but still allows them to be written on...
[T]he coating... made the paper waterproof without making it waxy, brittle or changing its other characteristics. The original piece of paper has been submerged in water since June... It hasn't dissolved and [Chief Chemist Sally] Ramsey's original writing is still on it. She once even took it out of the water, wrote on it some more, and submerged it again.
"It was kind of a 'MacGyver-ish' sort of thing," she said, referring to the 1980s TV series about a scientifically resourceful secret agent. "It turns out also that the paper greatly slows down the growth of mildew."
-- "Making paper waterproof--and writable", CNET News.com