I guess I missed this thread somehow
My pond is fiberglass, and I wouldn't have it any other way. Nothing better in my eyes. As stated earlier most of the stuff available for ponds are just coatings. They don't have much strength. But when your coating a structure like block walls, and such there isn't much of a need for strength. There is only 1/8" of fiberglass in the bottom of my pond (directly to the dirt) and on the walls. The walls of my pond were formed with 1/4" cement board. so my walls over-all are about 3/8" thick. There's not much else available that can compare to that and still have the strength that glass does. My pond, from start of digging to tossing fish in was a little over 2 weeks, and most of one of the weeks was rain. Took me a while to do the finsih stone work, but all in all it is a very fast and efficient product. Another nice thing, is if I wanted to double the size of my pond, I could digg out where I wanted, cut out the end wall, and start glassing again, and in a week or so, have a pond twice my original size. not much else will let you do that with that kind of speed.
Depending on the job, fiberglass is not that expsensive, my price to glass a pond is in the same ball park as polyurea.
I used to do tons of fiberglass fabrication, and all my work is hand layed fiberglass, no chopper gun here, that's why I can get away with only 1/8" of glass in my pond, it's a combination of using the correct materials and hand laying it.