I seen these block on Google Earth after following a link, they are close to Japan. One of the Islands next to it.

First I thought it might of been some ancient city or something weird but then remembered this is Japan, massive tsunamis. I guess that's what these blocks could be for. Although I am guessing entirely.

But as you can see here at some harbour on the same island close to Japan there is this weird harbour wall. Sure it might just be another harbour wall to protect from storms but I think it has to do with tsunamis protection as well. Although I am just guessing again.

Here is the Island I was talking about.