The postmaster of Sumami, Japan noticed that the city was somewhat lacking in tourism and he had an idea that would change all that. Postmaster Toshihiko Matsumoto altered an old, red post box that had been in the town since 1999 and put it near the coast of the fishing town hoping that the underwater postbox would attract divers from around the world.
He was right. The small town sees thousands of travellers each year coming into the local dive shop to buy waterproof postcards. Kioaki Yamatani manages the dive shop and he is the one who dives down to the underwater postbox each day, collects the notes and sends them to the post office.
The postbox has even been included in the Gunness World Records as the deepest underwater postbox at 10 meters and two post boxes are rotated every six months so they don’t get damaged by the seawater. You can see the video below: