Unbuki Underground Seawater Cave
This entrance to the Unbuki underwater limestone cave is about 400 meters from the coast. The saltwater inside is tidal, which indicates the presence of another opening under the seabed, but despite ongoing exploration by expert divers, this has yet to be found.
Formed by a collapse of limestone bedrock, the cave is reminiscent of the famous cenotes of Mexico, sinkholes which connect underground water sources to the surface. In fact, Unbuki is an anchialine pool, a landlocked body of water connected to the ocean by an underground cavern.
In September 2018, a team of expert explorers began surveying the site, confirming it as Japan’s longest underwater cave and discovering earthenware dated from the Neolithic period.
The team’s divers have found unusual sea creatures, including a new variety of shrimp, and filmed the first footage in Japan of the rare unbuki-anago, or Fryer's false moray eel. They believe there may be more unidentified species in this unusual habitat, but the key mystery of the undersea entrance remains unsolved. While other divers have since reached as far as 700 meters through the twisting passages, a considerable portion of which must run under the seabed, they have still been unable to find the connection to open water.
Please note that while visitors are free to explore the entrance and its surroundings, diving in the caves is prohibited.
