Purchase a heavy garden rake with metal teeth and a long handle. The teeth are likely to break if you use a regular leaf rake, and a light rake will skip over the water.
Slide pool noodle connectors onto the rake pole. Depending on the weight of your rake, you may need 2 or 3 of these. The rake should still be heavy enough to hook weeds but not sink below the water.
Attach the rope. You can use any kind of rope, but rope made for mountain climbing is waterproof, easier on your hands and lasts longer than other kinds of rope. Use duct tape to adhere about 2 feet of rope to the end of the rake pole. Wrap the rope liberally with tape.