JKUEP -Japan Karst & Underwater Exploration Project-

03/05/2026

【Minelayer "Tsubame" project is moving into its next phase】

The investigation of the minelayer Tsubame is now moving toward its next stage.

Based on earlier dives, collected documents, and the review of charted locations, several areas off Miyakojima remain important to re-examine. The next planned step is a sonar survey, allowing us to look at the site from a wider perspective and identify underwater targets more systematically before further direct investigation.

Personally, we don’t feel it’s necessary to insist on diving;
as soon as the sonar identifies a suspicious location, I plan to conduct an investigation using an ROV or underwater drone.
Once we’ve confirmed the presence of a shipwreck, I intend to proceed with the dive.

We will continue preparing carefully and moving forward step by step. Please keep following our work as this project develops further.

坪根 雄大
伊左治 佳孝

26/04/2026

【The dive to Nagara is starting to feel closer】

Preparation for the exploration of the light cruiser Nagara is steadily moving forward.

https://j-kuep.com/pj-nagara

This is not simply a plan to dive on a wreck. It is also an effort to document a place that carries history, memory, and the wishes of the people who have continued to remember it over the years. That is why the process matters as much as the dive itself. The coordination, the planning, and the careful preparation are all part of bringing this project into shape.

During those activities, we had the opportunity to meet Mr. Kojiro Nakahara, the grandson of Mr. Giichiro Nakahara, the captain of the Nagara.
We exchanged views on a variety of topics, including the challenges and significance of preserving history, as well as his feelings as a member of the bereaved family.

We will continue preparing with care, and we hope you will keep following our work as this project moves closer to the water.




森 裕和
Yosuke Ogiwara
伊左治 佳孝

20/04/2026

【ADEX Singapore and what it meant to us】
At ADEX Singapore, our founder Yosh*taka Isaji was honoured as Explorer of the Year in Asia. It was a great honour for us, but what left an equally strong impression was the scale and energy of the international technical diving and exploration community gathered there.

Important exploration and technical diving activities are already taking place in Japan. At the same time, we feel that Japan still has room to catch up with the wider overseas community in terms of network size, visibility, and the strength of shared momentum around exploration.

That is why this experience mattered so much to us. It reminded us that exploration is not only about going farther underwater. It is also about building stronger links with divers, explorers, and researchers across borders, and about creating a wider community that can support discovery, documentation, and collaboration.

We want to continue exploring and documenting underwater worlds in Japan while also expanding our connections with the international community. For us, ADEX Singapore was not simply an award moment, but an important step toward that future. Please keep following our work as we continue to build those ties.

08/04/2026

[We’ve updated our Akiyoshidai exploration page]

Beneath Akiyoshidai, Japan’s largest karst plateau, lies an underwater world whose full extent is still unknown.

We have updated the JKUEP page for the “Akiyoshidai Underwater Cave System Exploration Project” with details from our preliminary exploration at Terayama no Ana in February 2026, including the characteristics of the underwater passages we observed, the candidate sites for our next dives, and our plans for May.

https://j-kuep.com/pj-akiyoshi

When we actually entered the water, what we found was a world far more complex—and far deeper—than we had imagined.

We still do not know exactly what lies ahead, or where these passages may lead.

That is exactly what makes it so compelling.
That is exactly why we want to keep going.

For the next phase of the project, we have selected five caves as candidates for further exploration, including Terayama no Ana, where we conducted this latest dive.

How far can we push our understanding of the Akiyoshidai groundwater system?
We will continue this work carefully and step by step.

We would also like to express our sincere thanks to the cavers who supported us, to 清水 淳 for diving with us as a buddy, and to the landowners, the Mine City Akiyoshidai Science Museum, and everyone in Mine City who cooperated with this exploration.

DIVE Explorers

Akiyoshidai Underwater Cave System Exploration Project

11/03/2026

We have now completed this round of exploration on the World War II wreck "Tsubame".

One of the people who entrusted us with this mission, the son of Tsubame’s commanding officer, told us that he was simply glad that these efforts were being made at all. Hearing those words reminded us that this work matters—not only as exploration, but also as an act of remembrance.

Although we were not able to locate the main hull of Tsubame this time, we are already thinking carefully about how to improve our approach and increase the chances of finding it on the next expedition.

This exploration also received remarkable media attention. It may not be an exaggeration to say that journalists from every media outlet in Okinawa came to cover the project. Their response showed us just how strong the public interest remains in the history of the war and in those who were lost. We are deeply grateful to be able to contribute, even in a small way, to the ongoing efforts of remembrance and postwar historical work.

QAB (Ryukyu Asahi Broadcasting) aired a major feature on the project:
https://www.qab.co.jp/news/20260310286351.html

https://www.youtube.com/watch?v=Yl1yY_Ftek8

This expedition also highlighted something else that is very important for us

Students who learned technical diving at DIVE Explorers, operated by Yosh*taka Isaji who heads JKUEP, participated in this expedition.

From the beginning, one of our goals has been to create a path where divers who train with us can eventually take part in real exploration projects. As more people with different strengths and specialized skills join these efforts, we believe the scope and value of what we can achieve will continue to grow.

Thank you for cooparation!

2026年3月10日 放送　太平洋戦争当時に、宮古島の沖合で旧日本海軍の船が沈没しました。８０年以上が経つなか、艦長だった父親の遺骨を探したいという遺族の思いを受けてダイバーの男性が調査に乗り出しました。　宮古....

24/01/2026

We have received numerous requests from various quarters expressing interest in joining our expeditions.
Thank you for your interest.

We have created guidelines for participants in our expeditions and investigations.

https://j-kuep.com/application

Future explorations will also be posted on the same webpage.

Application Guildline

02/01/2026

We begin our exploration of Akiyoshidai, Japan's largest karst.

This is a major expedition in our work, and we look forward to seeing how it develops in the future.

【Akiyoshidai Underwater Cave System Exploration Project】
https://j-kuep.com/pj-akiyoshi

01/01/2026

In July 2025, we investigated the Hitachi Maru, the largest cargo-passenger ship at the time, which sank during the Russo-Japanese War.

The ship was sunk in the open ocean at a depth of 80 meters, making it a challenging dive, but we were successful in bringing back the results.

English
https://j-kuep.com/pj-hitachimaru

Japanese
https://tech-diving.jp/field/field-explore/pj-hitachimaru

Hitachi Maru Exploration Project

07/07/2025

We have posted the progress of our exploration of Chousei Coal Mine on our website.

We have successfully dived from the exhaust tower known as “Pier” and entered the mine shaft, and are now preparing for our next full-scale diving expedition.

For our next expedition, we are planning a maximum depth of 43 meters for 150 minutes, with a decompression time of 215 minutes, for a total runtime over 6 hours.

Thank for your interests!

Chousei coal mine skeletal remains salvage project

20/06/2025

We attempted to dive from a ventilation tower called Pier at the submerged Chousei Coal Mine and successfully completed our exploration.

We conduct this dive for salvage 183 skeletal remains.

For this diving attempt, we spent two months pulling up broken wood and pipes by hand from inside the peya.

Entering the mine shaft from the entrance which we found at the bottom of Pier, it was a sloping shaft that gradually descended to a depth of over 40 meters.

The visibility from the bottom of Pier to the mine shaft was about 30cm, but when we reached a depth of 40m, about 150m away from the bottom of Pier, saltwater mixed with the water and the visibility improved dramatically.

There were doors and gates blocking our path, but we overcame them and extended the line by about 250 meters this time.
The average water depth was 42 meters, so the bottom time was 100 minutes, but the decompression time required was also 100 minutes.

The total dive time for the next exploration is expected to exceed six hours.

According to the map which was made 80 years ago, the tunnel is over 5 km long, so we believe that further preparation is necessary to proceed any further.
We will continue to work on this project!

03/05/2025

The underwater caves and explorations of Minami-Daito Island that JKUEP and underwater explorer Yosh*taka Isaji have been exploring have been made into an NHK(Japan Public Broad Casting Company) TV program.

It is a surprise and a great pleasure to know that there are such beautiful underwater caves in Japan.
We hope that you will be able to see the beautiful underwater caves and our exploration through the TV program.

We would also like to thank all those who have cooperated with our exploration, research and filming so far.

https://tech-diving.jp/information/1158