A plurality of structural units for construction of eco-friendly structures in a body of water. A plurality of structural units comprises a primarily calcium carbonate material, preferably obtained from once living material from an organism, and a cement that is capable of holding the primarily calcium carbonate material. The plurality of structural units are of variable size and shape and are obtained by breaking up a larger portion of a composition formed by combining the primarily calcium carbonate material and the cement to hold the primarily calcium carbonate material.

A river training structure includes a longitudinal groyne placed in the river. The groyne extends in flow direction of the river with water of the river along both longitudinal sides of the groyne. The river training structure includes blocks, each block being constituted by a central part and four or more legs extending from the central part such that the central part and legs define a three-dimensional configuration allowing a multiple of said blocks to inter-engage with each other three-dimensionally when stacked onto each other. The groyne is constructed from a multiple said blocks irregularly stacked onto each other and engaging with each other to form a dam body of inter-engaging blocks, the dam body having a longitudinal slope at the navigation channel side of the dam body.

A system is provided for shoreline stabilization using a plurality of shoreline stabilization devices, having a base portion, which may be a solid structure or be formed from at least first two of the shoreline stabilization devices arranged in an end to end configuration on opposite sides of an imaginary line running perpendicular to the two shoreline stabilization devices; the base portion having a central protrusion or having at least one of the shoreline stabilization devices positioned perpendicular to and on top or in between the first two shoreline stabilization devices, and atop the imaginary line; and at least a second two of the plurality of shoreline stabilization devices each positioned on opposite sides of the imaginary line at an angle to provide at least two angled shoreline stabilization devices, forming an angle between a slope of between about 1.5:1 and 2:1.

The invention provides scour protection methods and systems comprising a plurality of units, wherein each unit comprises a concrete matrix having a pH of less than 12; and wherein each unit can interlock with another unit: wherein said systems promotes and enhances the marine biological fauna and flora at the proximity of offshore aquatic infrastructures.