Abstract: A multi-purpose marine structure intended to be submerged and installed on a sea bed. The structure comprises an outer peripheral body and a tapered inner section. The outer peripheral body is intended to be founded on a sea bed and comprises a tubular ring-formed body of concrete, the base of which is constructed and arranged to rest on a sea bed along its entire base periphery. The inner section is also of concrete and is formed as a cone or polyhedron having a lower end which is fixed to the outer peripheral body, the inner section tapering upwardly and inwardly from its lower end. The inner section and outer body together form a monolithic integral concrete unit, the inner section being fixed to the outer body along the inner periphery of the outer body.