With regards to osmosis in fiber glass products for use in a Koi pond, is the resign waterproof.?

My intention is to fiber glass a right angle edging strip arround the top of my pond and turf right up to the angled section which in turn will be sealed to the top edge of the pond. This edging strip is to prenent soil leaching into the pond when it rains. I am concerned about osmosis and wondered if the glassed product would have to be sealed in a specific way.