Just pouring bentonite into water will result in a sloppy, soupy mess of super slippery silt-like goo on the bottom, and will never seal. Bentonite has to be tilled into the soil at the proper rate, not too much and not too little. Then it has to be moistened and VERY tightly compacted in order to seal. And, if the bentonite dries out aeven a little too much, huge cracks form as the bentonite contracts, opening up huge holes for after to leak out of.