Please help with wood floor

I am seeking help about waterproofing my wood floors in the greenhouse. I bought a new “cabin” shed a few years ago with plywood floors and it had a couple polycarbonate roof panels. Now I want to convert it to a greenhouse but I have no idea how to waterproof the plywood floors. I don’t want mold or moisture anywhere on the floors of course. I’ve googled this, I’ve run about 100 ideas through my brain, but I think all roads lead to mold. I’m very allergic to mold and have no idea how to do a wonderful job. Anyone with experience and success on this issue? Thanks in advance!