Typology of Japanese concrete breakwater units.
The most famous is the "tetrapod" in 1st column, 2nd from the bottom.
But as you can see there are many, many others!
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When foreign tourists first visit Japan, they are often surprised to find most Japanese beaches are covered with these massive, interlocking concrete blocks, even in tourism destinations like Okinawa.
2/
The blocks supposedly prevent erosion, although numerous studies have shown they actually *increase* erosion.
The main reason more keep getting added is that they serve as a form of government handout to Japan's powerful cement industry lobby.
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Producing these blocks has become so profitable, that concrete companies frantically compete to concoct supposedly "better" new shapes in order to win lucrative government contracts to cover ever more of Japan's beaches for no actual reason.
Hence so many different types!
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It's estimated a staggering 50% of all Japanese coastline is now covered up with some sort of concrete armoring.
Again, research suggests this actually accelerates erosion, but Japan's concrete industrial complex remains undeterred, and new blocks are still being added.
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In Japan there are otaku for everything, so of course there are also otaku for breakwater blocks, who obsessively catalog all of the different shapes and sizes (making charts like the one above), and try to take selfies with every type of block in different parts of Japan.
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There are also people who find the blocks "cute" or even "sensual" and there are companies selling all sorts of tetrapod goods and even tetrapod plush toys called "tetogurumi."
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