Abstract: A marker bouy to positively mark positions on a water surface with respect to the bottom. The marker includes a generally hollow body with line wound around the approximate center thereof with a weight on the end of the line which will cause the marker to rotate when the marker is placed or thrown onto the water surface to cause the line to unwind from the marker. A line stop flange is provided on the marker to stop unwinding of the line when the weight strikes the bottom. This flange comes into effect when water partially fills the marker which will cause the marker to shift from a position of lying on the water surface to being erect within the water. When the marker is in the upright or erect position, the line is engaged by the line stop flange. When the marker is in this erect or upright position, one end will be above the surface of the water and therefore easily visible.