waterproofing a waterfall
I have discovered that the the edge of the liner rising up from beneath my waterfall is too low. The water fall is made of very large rocks on both sides and sits on a large plate of slate. It would not be difficult to waterproof the inner surface and floor if I could remember the substance to use. I believe that at one time I was told that a clear waterproofing coating was available, maybe it is fiberglass? I would prefer not to take the waterfall apart because the stones are huge (small boulders). I know that it is possible that in the future I may have to take the thing apart and put in a different liner. I was at work when it was installed. I requested that the edges of the waterfall liner come up at least 12" (I am weird like that, I like my liner high with extra).
Can anybody tell me what this coating is called?