We used a 4in. gold dredge,riffles and all and floated a 2 ft x 3 ft wooden frame with sides and bottom covered in 1/4 in hardware cloth. Dredged at Marinas, Docks and swimming areas. The riffles will let the halves and quarters drop out in the sluice and the gold rings and chains also. Dimes will not pass through the 1/4 in. hardware cloth and the floating catch basin will keep all broken glass etc. from going back in the water. Never had problems with marina ,swimming area owners after we showed them all the broken glass, trash, etc that we were removing from their location. IT IS WELL WORTH THE EFFORT to get permission to dredge these locations. At one old dock where they gassed up the boats,built in 1940, we took out literaly hundreds of siver coins, 2 diamond rings and over 300 dollars in clad coins. Still looking for another like it! Fall is the best time, no one swimming to get in the way. Just be sure to give the owner a sample of your silver,we gave 2 each of halfs,quarters,and dimes and haul off all trash. Now is the perfect time . Good hunting.