Postcrossing Blog

We’ve written before about the Underwater Postoffice in Vanuatu, and we thought at the time it was the only place you could post a letter underwater in the world.

Well, turns out that isn’t quite true! Postcrosser Cindy (aka cindybeaule) let us know about an underwater post box in Susami, Japan, which was put in place in 1999 as part of a fair to promote the Kumano Kodo pilgrimage trail. It’s a collaboration between the former postmaster, a man called Toshihiko Matsumoto, and the local diving community. Waterproof postcards are sold in the dive shop, and you have to write your message using waterproof oil-based markers, so the message won’t wash off.

You need diving gear to even reach the post box, because it’s 10 metres below the surface. It’s actually in the Guinness Book of World Records because it’s the deepest post box in the world, and they have a certificate to prove it! The boxes are made of cast-iron, so there are actually two used in rotation, so they can be cleaned and repainted.

I even did some more poking around, and it turns out there are a few other underwater post boxes. There’s one in the Malaysian island of Mataking, another one in the Jemeluk Bay Underwater Gallery in Indonesia, and two “dry” ones: an underwater observatory in the US Virgin Islands and the Risør Underwater Post Office in Norway.

You can watch a whole mini-documentary about the post box in Susami on Youtube—we were amazed to learn that there had been over 38,000 special waterproof postcards sent from this underwater post box at the time it was filmed in 2018. I wonder if any Postcrossers have ever sent or received a card from Susami…? Do let us know!