This is similar to what we used. Multiple occasions/ponds.
Several where there was a sand member that was leaking in several feet of water. We used a combination of placing the sacks on the bottom near the sand and cut it open and dumped the contents and also placed some in buckets , added a little water and poured over the area. The flow of the water pulled the mix and slurry to the leaking sand. Amounts vary depending each site. Ponds were from 4 to 10 acres. Average about 20 bags and it took a week or so to stop leaking. Normal type ponds 8-12 ft at the dam with most area 3 ft deep, avg. depth probably 4 ft. Most of the ponds were new < 2 years. Did not try to quantify the water vol. loss.
They now have bentonite drilling mud with polymers in the mix.