Abstract: A marker buoy is provided for use with a flexible line tied to a weighted sinker. The buoy includes a watertight, transparent dome assembly with an interior light source positioned therein. The dome assembly resides on a buoyant housing with a bottom aperture and line guide for receiving and guiding a flexible line for winding on a reel assembly positioned within the housing. The reel assembly utilizes a spiral coil spring that is wound as the line unwinds from the spool and acts to return excess line to the spool as the sinker attached to the line comes to rest on its intended submerged surface. In one embodiment a reduction gear is provided to increase the number of spool turns available before the spring winds completely.