Select a long-lipped, deep-diving plug, such as the Mann's Stretch 30 and 40, or Rapala's X-RAP Magnum 30, and remove the hooks.
Secure the plug to 20 inches of 920-pound cable crimped around a thimble to the split ring or eye of the plug.
Crimp the opposite end of the cable onto one eye of a 500-pound-test, three-way swivel.
Attach the 300-pound-test ball-bearing snap swivel on the dredge line to the eye adjacent to the one carrying the swimming plug.
Secure a 30-inch length of cable to the third eye, and crimp another 300-pound ball-bearing snap swivel to its opposite end, and fasten this to the dredge.