The rectangles in the water are oyster farms; the boats are collecting the days harvest. E.g., see the following;

http://www.lib.noaa.gov/japan/aquaculture/exchange/ustrip2000.html

The pictures really don’t do the Mijajima area justice in Google Earth! I would highly recommend it to anyone visiting the Hiroshima area. Just be prepared to be hounded by the local deer population that will literally steal food from the hands of unwary pass-by’s. Not to mention residents of the monkey colonies near the top of Mount Misen that will steal pretty much anything. The local English language signage is clearly written by someone with a sense of humour, whether it is the “8 minutes to the cable cars, or 6 if run a little”, the quaint “beware of the monkey” signs, or the simply badly spelt “free rockers” for storing your possessions to keep them safe from the marauding deer and monkeys;

http://realtravel.com/miyajima-reviews-a4452373.html

Rather more sinister in the area, 10 miles across the bay to the North East is the Hiroshima Prefecture Industrial Promotion Hall. This building was quite literally blown up in the atomic explosion of 1945 (hence it’s other name, the A-Bomb Dome). The ruined hulk has been left as a memorial to future generations as to the horrors of war…

Placemark: Google Maps / Google Earth

http://www.richard-seaman.com/Travel/Japan/Hiroshima/AtomicDome/index.html