I didn't want toasted celery if my insulation proved lacking. There are some good articles on waterproofing on the web with some different takes on the ways you can go about it.
Most people use some type of commercially available conformal coating.
However, there's always someone who goes about things in a unique way. After reading the ingredients of the different conformal coatings, I found that a number of them were polyurethane based compounds. Having just done a refinish of our hardwood floors a while back, I happened to have some poly made by a company called Deft. I coated an old circuit board with it and not surprisingly it worked great. The board belonged to a digital multimeter with a bad ammeter shunt and it worked as well as I could have asked for while submerged in water up to the display.