According to one preferred embodiment, the present invention can have a housing with a cap on one end. A flag support and a flag can project from the cap. A sleeve can be movable between the ends of the housing. A mechanical assembly is contained within the housing, and includes a rod, a plug, a tensioner and a reel. The tensioner can control the amount of tension on a line that is dispensed from the marker buoy. The line self-dispenses under the load of a weight connected to the line. The sleeve, operable in a first position, helps to maintain a vertical orientation of the housing within the water. Yet, the sleeve in a second position can prevent unwinding of the reel and maintain the flag in a storage position.