Another option is a "poor mans downrigger" its old school, and you don't see it that often, but it works just fine. Just use a spool of small diameter rope, put tape on it every 10 ft to indicate depth, and just attach it to a cannonball. Lower it over the side to the desired depth then use a 5 gallon bucket or flower pot to coil the line up as you raise it. Perfect for lake fishing.