Humanity's fascination with the undersea world is evident from the popularity of works such as Jules Verne's 20 000 Leagues under the Sea, in the numbers of people who participate in sports such as snorkeling and scuba diving, and in the length of line-ups outside of aquariums. It should be no surprise that over a period of more than eighty years, several fundraisers, promoters of tourism, and postal administrations have realized that they can use unusual underwater mail facilities as lures to catch novelty-seeking stamp collectors. This website documents six such facilities found around the world.

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The "Sea Floor" Post Office in the Bahamas

Susami Bay Mail Box, Japan

Green Island Mail Box, Taiwan

Underwater Mail Boxes in Sabah, Malaysia

Risor, Norway's Underwater Post Office

Vanuatu's Underwater Post Office at Hideaway Island

Although I am not aware of any underwater post offices in the United States,
the 2026 Postcrossing Global Postage Commemorative depicts a scuba diver who
seems to be searching for a mailbox in which to deposit a post card in his hand.