An artificial reef for coastal protection comprising an useful energy-generating unit suitable for capturing simultaneously the kinetic energy and the pressure differential energy resulting from difference in water heights between the waves crest and trough, converting them into useful energy, and further comprising: • at least one upper conduit and at least one lower conduit, which are juxtaposed and parallel to the direction of waves propagation as well as hydraulically connected, both comprising apertures, wherein: o the apertures located in the at least one upper conduit consist of entries and the apertures located in the at least one lower conduit consist of exits, o each of said entries and exits comprises filtering and reflux control elements which in turn comprise a filter and means for controlling reflux, suitable for limiting the water exiting via the entries and limiting the water entering via the exits, characterised in that: • the at least one upper conduit is provided with curved directrices converging towards the entries, and said curved directrices of the at least one upper conduit being such that change the direction of horizontal flow under the wave's crest transforming it into a concentrated flow driven towards the entries, thus harnessing the kinetic energy from the wave's crest to push the water into said entries; • the at least one lower conduit is provided with curved directrices diverging from its apertures, which consist of exits, and said curved directrices of the at least one lower conduit being such that change the direction of the outgoing flow transforming it into a flow having precisely the direction of the natural flow under the wave's trough, thus harnessing the kinetic energy from the wave's trough to suction the water out of said exits, • said useful energy-generating unit provided with a shut-down valve, which is configured to automatically close in case of storm in such a way that the artificial reef acts as a reef by inducing the pounding of high waves passing above it, and to automatically opening again after the storm has passed in order to allow the flow from the at least one upper conduit to the at least one lower conduit and thus being further configured for actuating the useful energy-generating unit through a direct contact with the said sea water flow • legs with a length suitable for convenient adjustment of an height of anchoring to the seabed. • at least one upper conduit and at least one lower conduit, which are juxtaposed and parallel to the direction of waves propagation as well as hydraulically connected, both comprising apertures, wherein: o the apertures located in the at least one upper conduit consist of entries and the apertures located in the at least one lower conduit consist of exits, o each of said entries and exits comprises filtering and reflux control elements which in turn comprise a filter and means for controlling reflux, suitable for limiting the water exiting via the entries and limiting the water entering via the exits, o the apertures located in the at least one upper conduit consist of entries and the apertures located in the at least one lower conduit consist of exits, o each of said entries and exits comprises filtering and reflux control elements which in turn comprise a filter and means for controlling reflux, suitable for limiting the water exiting via the entries and limiting the water entering via the exits, • the at least one upper conduit is provided with curved directrices converging towards the entries, and said curved directrices of the at least one upper conduit being such that change the direction of horizontal flow under the wave's crest transforming it into a concentrated flow driven towards the entries, thus harnessing the kinetic energy from the wave's crest to push the water into said entries; • the at least one lower conduit is provided with curved directrices diverging from its apertures, which consist of exits, and said curved directrices of the at least one lower conduit being such that change the direction of the outgoing flow transforming it into a flow having precisely the direction of the natural flow under the wave's trough, thus harnessing the kinetic energy from the wave's trough to suction the water out of said exits, • said useful energy-generating unit provided with a shut-down valve, which is configured to automatically close in case of storm in such a way that the artificial reef acts as a reef by inducing the pounding of high waves passing above it, and to automatically opening again after the storm has passed in order to allow the flow from the at least one upper conduit to the at least one lower conduit and thus being further configured for actuating the useful energy-generating unit through a direct contact with the said sea water flow • legs with a length suitable for convenient adjustment of an height of anchoring to the seabed.