i've always been skeptical of water application methods but if you can have success at $3500 for a 3/4 acre pond without draining, amen. if the leak is localized and relatively strong i can see how it might draw in the bentonite to plug itself, but if its a widespread area that is seeping, in my mind, the best fix is a drain, add clay, til it in, compact, and let it fill again...FWIW.
