This has to be the mother of mysteries. Susami, a fishing town in Japan’s Wakayama prefecture holds the record for the deepest underwater postbox, at a depth of 10 metres.
In 1999, a postmaster of Susami which then had no attraction, proposed the underwater postbox which came to be recognized by the Guinness Book of World Records as the deepest in the world. Due to corrosion by sea water, two boxes are used in rotation every half year to protect the postbox.
The town’s underwater postbox is now an attraction and more than 1,000 divers go to deposit water-proof mail in it every year.
It is also a good place to … well, if you’re young especially, rack up a lot of likes for your Facebook and Instagram photos.