In trying to keep the erosive force of the ocean at bay, we often end up simply throwing materials at the shoreline. Rocks are the most common candidate employed for breaking the action of waves, although other approaches are used – including the deliberate wrecking of ships (such as at the brilliantly-titled Aramoana Mole near Dunedin).
In places, concrete units of varying geometries serve this role. Some take the form of simple cubes or pyramids (such as at Greymouth, pictured below) where pyramidal units hold the side of a breakwater), whilst others have more complex, interlocking forms that give them an appearance akin to a giant game of knucklebones. Some of these complex types are called tetrapods (due to the four ‘feet’, which are really shallow prongs, that make them lock together), whilst another variant is the akmon (pictured above, adjacent to Wellington Airport)– a form that is named after the Greek word for anvil (an analogy that is blatantly apparent when one views these impressive units upon our coastlines).