Abstract: Apparatus and method for constructing an artificial ocean reef for use below the ocean surface to serve as an offshore breakwater for inbound waves and thereby prevent beach erosion. The reef has a plurality of adjacent sections, each of which comprises an arched wall having a series of side-by-side transverse concrete blocks, and flexible interconnections between the blocks at adjacent lateral edges to provide a generally smooth outer surface. The arched wall sections are each formed above the water surface on a barge or the like and then submerged with a shoreward side having a shoreward end resting on the floor of the ocean and a seaward side with a seaward end resting on the floor of the ocean outwardly from the shoreward end to present the smooth outer surface on the seaward side of the wall to incoming waves. Adjacent sections are secured together to form a continuous barrier aligned with the shore line of the beach being protected.