Connecting Through Their Inquisitive Spirits: Diver Akira Kubo and Planner Tetsuya Miyake Discuss the Ryusendo Cave Survey and Diver 1964 2nd Edition

October 2, 2023

Ryusendo Cave in Iwaizumi, Iwate Prefecture, is regarded as one of Japan’s three great limestone caves. Yet to be fully explored, the limestone cave has attracted the interest of divers both in Japan and abroad. Diving surveys of Ryusendo Cave first began in the 1960s, after which they were inevitably halted twice due to an accident and a natural disaster. This April, the survey was resumed for the first time in roughly six years. Three divers took part, including Akira Kubo who has been serving as Survey Captain since 2009. Mr. Kubo speaks to Tetsuya Miyake, who is in charge of product planning for ORIENT and Orient Star, about this new challenge of exploring the cave in its entirety.

Text: with ORIENT STAR editorial team



"Aiming for Authenticity" – Meeting Mr. Kubo for the First Time


-- This April, a diving survey of Ryusendo Cave was carried out for the first time in six years. Mr. Kubo, you served as Survey Captain. What was the objective of this survey?

Akira Kubo (hereinafter “Kubo”): There were three main objectives. The first was to survey the underwater algae. Seven or eight years ago, the underwater lighting in the cave were changed from lightbulbs to LEDs. We wanted to check whether this had affected the volume of algae, or whether new algae species had grown as a result. The second was to check the underwater condition, as the water had risen several times in the past six years or so. This was mainly to collect preliminary information before starting a full-scale investigation inside. And lastly, we needed to test new diving equipment.

Miyake: What was it like diving there for the first time in six years?

Kubo: Somewhat nostalgic. I felt like saying, “Hi, I’m home.”

Akira Kubo, diver and survey captain of the diving survey conducted in Ryusendo Cave this April. Also a pioneer of the DIR (Do It Right) diving philosophy that prioritizes safety.


-- Mr. Miyake, I heard you have a close friendship with Mr. Kubo. How did you two meet?

Miyake: Until two years ago, I was in charge of development in the Design Department. One of the things my team was working on was the advanced development of divers’ watches. Divers’ watches are worn as a fashion item by many people, but they still have to be able to withstand harsh environments like a full-fledged divers’ watch, not only in terms of water resistance and robustness, but also visibility, ease of use, and wearing comfort. There were many things about diving that I couldn’t figure out simply by working at my desk, so I knew I had to talk to a professional and hear their thoughts. Also, rather than normal diving, I was more interested in finding out everything I could about cave diving, which is said to be the most extreme and dangerous type of diving. That’s what I was working on when, one day, I happened to meet Mr. Kubo at a diving symposium.

Kubo: It was a symposium hosted by the Japanese Academy of Underwater Sciences.

Miyake: The symposium was full of various presentations and discussions about safe diving and environmental protection. Afterwards, I happened to exchange business cards with Mr. Kubo who was a board member of the Academy, and that’s when I found out that he was an authority in cave diving. So, I offered him a post as an advisor, which basically means that we ask him to wear our sample watches on diving trips and ask for his advice.

Tetsuya Miyake, a member of Seiko Epson’s Wearable Devices Business Division who currently serves as Product Planning Manager for both ORIENT and Orient Star. He led the planning effort for Diver 1964 2nd Edition released this June.

-- Is this why Seiko Epson sponsored the recent diving survey?

Miyake: That’s right. We wanted to gain feedback on products we developed by having someone actually wear them inside the cave. Also, since Ryusendo Cave is a source of water for the local community, we felt that carrying out a survey and protecting the environment there would be a meaningful contribution to society.

Kubo: The local residents were delighted by our recent activities. For the town of Iwaizumi, Ryusendo Cave is highly valuable both as a water source and a tourist attraction. The town mayor thanked us not only for the environmental protection survey, but also for promoting the Ryusendo Cave by name and making a watch inspired by it.

“Black Underwater, Green on Land”


Miyake: There was one particular question I wanted to ask today. Diving technologies and methods are being updated on a daily basis, but is the same true for the Ryusendo Cave survey?

Kubo: Yes. Back in the 1960s when the survey first began, diving technologies were still very poor. For example, tanks we use today contain a gas mixture compressed 200 times – that’s 200 bar. But back then, tanks only contained air, so no matter how compressed it was, it only ever reached 150 bar. This was partly because compressors didn’t perform as well as they do now: tanks nowadays not only enable longer dives, but the use of gas mixtures or oxygen-rich tanks with highly concentrated oxygen reduces the time it takes to decompress during ascent, and the risk of decompression sickness is also very low.
Also, divers back then used regular rope to dive everywhere. We now use what’s called a cave line to mark our way back so that we can return safely.

Miyake: They used to use normal rope? Did they have to wind it all up when they swam back?

Kubo: The rope was hooked to a yellow piton hammered into where we call the "natural bridge", about 40 metres underwater. Actually, it’s still there.

A cave line used by divers today. During dives, lines like this are used by divers to mark a path so that they don’t get lost. At key locations, they hook markers with the diver’s initials on them, or notes written on waterproof paper, onto the line.

Miyake: I see. The Diver 1964 2nd Edition released by Orient Star this June is based on the design of the Calendar Auto Orient, a model released in 1964 as the name suggests. But rather than simply reissuing an old model as is, we updated it with our latest technology to enhance water resistance to 200 meters, making it compliant with ISO 6425, the international standard for divers’ watches. We plan on adding more new technologies and ease of use to this design to create an even better divers’ watch.

Kubo: There were two pieces of equipment I tested during the recent Ryusendo Cave survey: one is a new diving computer, and the other is this divers’ watch. One thing I managed to confirm while wearing it in the cave was its excellent visibility. Luminosity is used to read a watch in the darkness of the water: first, you shine a light on the watch for a while and move it away. Then the hands and scale continue to shine brightly due to the luminous paint. I’ve used many divers’ watches in the past, but I found that this watch has great luminosity, making it very easy to see.

Miyake: Visibility in the dark is also strictly stipulated by ISO standards.

Kubo: Another positive aspect was the small size. I liked how the watch fit comfortably on the wrist of a person on the smaller side like me, and that it didn’t get in the way of movement. During a dive, I usually wear a diving computer on my right arm and control a BCD (buoyancy control device) – a device that controls buoyancy by adjusting the volume of air and gas – with my left. A watch that’s too big might catch or bump on something while I navigate through the water, and if it’s too heavy, it becomes a source of stress.

Miyake: Is weight noticeable even underwater?

Kubo: It is when you move your arms around. But the size and weight of this watch didn’t bother me at all.

Miyake: I think the same thing can be said for regular use. These kinds of factors, like not being too big nor heavy, are an advantage in harsh conditions, and are also beneficial for daily use. It was very important for us to have Mr. Kubo identify these advantages through actual use.
The model he wore while diving had a mirror-polished black dial, but we also created a model recreating the mysterious green colour of Ryusendo Cave. It’s this model here, with a green gradation on the dial.

To recreate the mysterious green of Ryusendo Cave, repeated trials were carried out not only for the colour, but for the extent of the gradation effect as well.

Kubo: There’s the gradation effect, coupled with what looks like an almost blueish green colour. I think it very closely resembles Ryusendo Cave.

Miyake: There are many different shades of green, so it took some effort trying to work out which green to use as the base colour, and how much gradation to apply. It’s easy to imagine the finished look of a single colour because we have samples of them, but with gradation, you really don’t know how they’ll turn out until you try it. So, we created several gradation samples to narrow down our choices. It was also hard deciding on the combination of dial and bezel colours. It took a lot of trial and error on everyone's part, but in the end, I think we managed to create a mysterious dial that draws you in, just like Ryusendo Cave.

Kubo: It does feel like it draws you in. I’m actually thinking about owning two of these watches: I’ll wear the black one when I go into the water, and the green one on a daily basis, on land. That way, I’ll always feel the presence of Ryusendo Cave by my side, and I think the colours will be a good conversation starter.

Diver and Watchmaker Resonate Together with their Inquisitive Minds


Miyake: What did you achieve in this recent diving survey?

Kubo: One of our objectives was to survey algae, but when we actually went down, we realized that there wasn’t all that much of it. We did find a small amount growing on the guide line, right where the light hits, so we took some back with us and handed it over to the researchers. Also, part of the guide line was missing, which we managed to replace. Maybe when the water rose, muddy water flowed in all at once and unhooked part of the line.

Materials collected from previous Ryusendo Cave surveys. The challenge is to reveal the full extent of the cave based on various data such as overhead and cross-sectional diagrams. It hasn’t been decided when the next survey will be, but Mr. Kubo says, “I’m already working on a lot of ideas in my head.”

Miyake: Has the recent survey changed your thoughts on Ryusendo Cave?

Kubo: It has. When I was first approached with this project in 2009, I was primarily driven by my curiosity as a diver, because it’s such an interesting place that very few divers have been to. However, as I went on more and more dives there, the local townspeople began to bring me homecooked meals or give me words of encouragement when I saw them in town, and this was the case on my recent dive, too. I also began interacting more frequently with people from the town office.

Miyake: The whole town is behind you.

Kubo: I’m so thankful for their support. The recent dive reconfirmed my belief that the Ryusendo Cave survey isn’t just about satisfying our curiosity as divers; there is a larger mission of helping the town maintain and refine the town’s asset. I was reminded once again of the importance of my role in contributing – in various scopes and values – to the Speleological Research Institute of Japan which has been researching Ryusendo Cave from early on, to the town, and to the environmental conservation efforts. Now, my interest lies in making sure that people in the future will say, “I’m glad I entrusted you with this survey.”

“I want to wear the green model when I’m on land,” says Mr. Kubo. The watch lends a refined accent to his shirt-and-tie look.

Miyake: This is a little off-topic, but one of Orient Star’s themes is outer space. And I’m always working on various product ideas based on stars, comets, and constellations. The new divers’ watch is based on the deep and mysterious world of the Ryusendo Cave. Like outer space, there are still many unknowns when it comes to the bottom of the sea, as well as Ryusendo Cave. This might sound like a stretch, but I feel as though people are still tackling the frontiers of outer space and underwater, which are both extreme conditions, and they share a common sense of curiosity towards the unknown.

Kubo: You’re right, it’s very similar. Both are about venturing into places with no air, and there are similarities in the terms “aquanaut” meaning divers, and “astronaut” meaning people trained to go to space. Actually, one thing happened that left a strong impression on me. When Orient Star was developing the divers’ watch, you once asked me to come into the Seiko Epson office to talk to employees about what diving is all about, so that everybody working on the divers’ watch could learn more about it. Needless to say, everybody listened intently to my talk, but what left a strong impression on me was the sheer number of questions they asked afterwards. I took some diving gear with me, but I was bombarded with questions like “How do you use this?” and “Why do you need it?”

Miyake: (Laughs) It’s true, our members are an inquisitive bunch.

Kubo: That’s when it struck me that your company must truly value the act of creating products. I felt like it gave me a glimpse into the curious nature of people who make things. It may be different from the curiosity of us divers, but it feels similar in origin. It made me reaffirm my belief that I was right in choosing to help with this project, and I felt glad to be a part of it.

Miyake: Our company has been making watches for a long time, and even taking the divers’ watch alone, we’ve continued to hone various features like water, dust, and shock resistance through development. I feel like our interest in pursuit and exploration is built into the company’s DNA. At times I wonder if we’re being too particular or too tied down to the idea, but it’s something that forms the basis of our watchmaking and we should probably continue to protect it.

-- It’s interesting how a diver and a watchmaker, two completely different professions, managed to bond through a shared inquisitive spirit. Our conversation today showed just how meaningful your collaborative relationship is. Thank you for your time today.

Miyake: Thank you for another interesting and valuable conversation.

Kubo: Likewise, thank you.

Akira Kubo. Representative of DIR-TECH Diver’s Institute. He first began diving at the age of 21 and moved to the US to study when he was 46. While majoring in international environmental policy, he also studied diving safety and became Japan's leading expert in this field. He has been serving as Survey Captain of Ryusendo Cave surveys since 2009, when diving surveys were resumed. Born 1953.

Tetsuya Miyake: Member of Seiko Epson’s Wearable Devices Business Division and WP Strategic Planning Department. In charge of product planning management for ORIENT and Orient Star.

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