Finnally something I have knowledge of. Dolosse were invent in South Africa many years ago, but they are only one type of concrete block for wave dissipation and protection. Many others exist and some of them are patented and require the payment of royalties to be used. Anyway, in Portugal we do not use dolosse ever. We used it once in Sines deepwater breakwater, which suffered a catastrophic collapse in 1979. The promise of dolosse is that the blocks work together because of their shape and thus the individual block can be lighter and cheaper. This does not work in practice, at least in high energy seas. The ocean is unforgiven. What happens is that if only a few blocks break the whole structure will quickly collapse during a storm. And things can break due to a series of problems and risks. Concrete is only good at resist compression stresses and reinforcement with rebar is almost always a bad idea in ocean conditions, so complex shapes are hard to make and to move without introducing unwanted stresses that reduce the design strength conditions. Other types of blocks rely mostly on their design weight and density, and the shape is just used for increasing energy dissipation and overtopping. For example, tetrapods can be moved with only compression forces on the block.