Divers Discover Prehistoric Landscape in Japan’s Deepest Underwater Cave

Mar 23, 2026 | News On Japan

OITA, Mar 23, 2026 (News On Japan) - A team of divers conducted an investigation toward a depth of 100 meters on March 20th inside the Inazumi Underwater Limestone Cave in Bungoono, Oita Prefecture, where a landscape dating back hundreds of millions of years is believed to remain untouched.

The cave, thought to have begun forming around 300 million years ago, contains narrow passages barely wide enough for a single person, forcing divers to carefully advance deeper into the submerged cavern.

After approximately two and a half hours, diver Yuji Ohama, who took part in the survey, described the experience as traveling through time. "It felt like riding a time machine made of water and witnessing an incredibly ancient landscape. I was able to see a place no human has ever seen before, and it was deeply moving," Ohama said.

Although the team did not quite reach their target depth of 100 meters, they descended to 97.4 meters, marking a significant achievement in the exploration.

The depth reached could potentially qualify as the deepest point recorded in a limestone cave in Japan, and the team plans to apply for official recognition with the Japan Record Certification Association.

Source: FNN

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