Mooring Buoy Cast Iron Sinker
sinkers are adequate to keep buoys in their assigned positions. They do not provide the resistance or holding power of anchors of the same weight but have the great advantage that they will provide the same resistance irrespective of the direction that the mooring load is applied.

Sinkers may be made of concrete, cast iron, rock or bundles of used chain.

The effective sinker weight will be equal to the weight of the sinker in air minus the weight of the water displacement, that is roughly 66% of Air weight.

Rock Sinker can be made by fixing a mooring eye in a piece of rock, or large stone. This may be effective if there is a local supply of dense stone in suitable sizes. However, it is very difficult to assess the condition of an individual rock and it can break in service. Now a days it is an ancient system and no way stable and trustworthy and many accidents occurred due to this type of Sinker.