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Imagine descending beneath the tranquil waters of Susami Bay in Japan, not for a treasure hunt, but to mail a letter. Here, ten meters (33 feet) below the surface, a fully functional postbox offers a truly unique postal experience. Enthusiastic divers can purchase special waterproof postcards and, armed with oil-based markers, pen their messages before submerging to deposit their greetings into this submerged red mailbox. It's an extraordinary way to send a message, transforming a simple act into an unforgettable adventure.
This remarkable underwater postbox was originally installed in 1999 as part of the Nanki-Kumano Experience Expo, an initiative proposed by Toshihiko Matsumoto, the town's then-70-year-old postmaster. His innovative idea aimed to draw tourists and divers to the scenic Susami region. The postbox quickly gained international recognition, earning a spot in the Guinness World Records as the world's deepest underwater postbox. Local dive shop staff regularly retrieve the mail, carefully drying the postcards before ensuring they reach the conventional postal service for delivery to destinations worldwide.
The quirky attraction has proven to be a resounding success, with an impressive 1,000 to 1,500 pieces of mail collected annually. By 2018, nearly 38,000 letters had been sent from this submerged station. To withstand the constant underwater environment, the postbox undergoes regular maintenance, including repainting every six months and a complete replacement with an unused mailbox each year. Some local businesses even offer edible and flavored postcards, adding another layer of novelty to this already bizarre and beloved geographical landmark.