Susami is a small Japanese fishing town, two hours by express train from the city of Wakayama. Until 1999, no one knew or cared about it. To change that, the then postmaster Toshihiko Matsumoto came up with an idea: a mailbox under water! Sure enough, the idea made waves, and Susami made it to the Guinness World Records.
The mailbox sits 10 metres under water. Between 1,000 to 1,500 pieces of mail are dropped into it each year. The postcards are water-resistant, and messages are written with an oil-based paint marker. Once every few days, a bunch of divers collect the mail and take it to the local post office. Letters are then delivered to recipients within a week of being posted.