only thing i use is a "pond rake" a friend gave me. came from a golf coarse. probably a little expensive to buy, but mine was a gift. works good, but is a lot of work.
basically its a heavy duty aluminum 3 foot rake attached and braced to about a 6 foot handle. it has an aluminum box mounted above the rake that you can put sand in to give it weight for bottom raking, or leave empty for dragging surface or shallow water. it has ropes that can attach at end of handle and at either end of rake. you throw it out and drag back with ropes. i usually just use rope at end of handle. could be attached to boat handles, but havent done that yet.
happy dredging.
