This is a good example of the maintenance- impairment I mentioned earlier. There were several stretches like this, which may be no problem for a mountain bike but are slippery death for a road bike; they pretty much involve walking the bike until the sand stops and the pavement returns.
If you've been on the Shimanami route (described in detail on this site), you're probably no longer surprised to see bridges exclusively for bicycle and pedestrian traffic. But this cyclist still finds it pretty spectacular. There are several such bridges along this route, including this massive one. Eventually, bridges will link all of the coastal sections of the route, but for now you'll have to content yourself with detours in some cases.