This is a watch review. It just so happens to be one that involved staying three fathoms beneath the surface of the sea, overnight.
I recently stayed at the Jules Undersea Lodge, the current iteration of what once was La Chalupa, an undersea living habitat that was part of the Puerto Rico International Undersea Laboratory program. PRINUL kicked off in 1972, squarely in the middle of the golden era of Man in the Sea research programs that saw aquanauts living and working at depth studying marine ecology, diving physiology, and ocean engineering. Four aquanauts at a time occupied the La Chalupa habitat, which was submerged in 20 meters of water off the coast of Puerto Rico the year PRINUL started. The objective of the program was to answer the question: Can humans live and work in the sea?
The PRINUL program ran out of funding and was forced to wind down in the late 1970s, but Ian Koblick, the father of the La Chalupa habitat, found a second life for the vessel in the ’80s as Jules Undersea Lodge, now essentially an underwater hotel.
The habitat is shaped like a barge, so when the ballast tanks were pumped all the way up, it could be towed behind a vessel floating on the ocean surface. It made the journey from Puerto Rico to Key Largo, where it’s now submerged at 30ft deep in a mangrove lagoon. It’s been outfitted with creature comforts; basic amenities like carpeting and a TV have been installed.
Aspiring amateur aquanauts can dive down and stay overnight in the habitat. The entry hatch is right at 20.5 Feet of Sea Water (FSW), and it varies +/ – 1FWS, depending on the tides. This is the depth your body “sees” physiologically for the extent of your dive because the habitat is pressurized to 20.5 feet. I kept double-checking my depth gauge because it read 21 feet deep long after I exited the water and doffed the SCUBA gear inside the habitat. It was surprising to see it read accurately without being submerged in water, but it’s the compressed air inside the habitat that it’s reading. After 11 scientific missions at 60 feet in the ’70s and thousands of dives after it was converted to a hotel at 30 feet, the folks operating Jules Undersea Lodge (Koblick is still heavily involved) have the whole thing down to a science.
Enter Japan’s mack daddy dive watch, the Grand Seiko SBGH255. This 600m-rated professional model is designed with saturation diving in mind. After 18 hours in the habitat, my body became saturated with nitrogen (the body will on-gas to reach equilibrium at depth), therefore allowing me to experience my first saturation dive with the SBGH255 on my wrist.
A Primer On The SBGH255
The SBGH255 is the superlative dive watch made by any organization in the Seiko Group, and it comes from subsidiary Grand Seiko, responsible for creating watches with the highest level of technology and finishing throughout the whole group. The entire watch is constructed from Grand Seiko’s high-intensity titanium with signature zaratsu polishing, and inside you’ll find the hi-beat 9S85, a premium caliber that oscillates at ten beats per second and is accurate to +5/-3 seconds per day.
According to Grand Seiko’s product planning team out of Tokyo, the SBGH255 features a dial that’s distinct from other divers, even within Grand Seiko’s own range. In an email interview, the team told me that “usually, to achieve high levels of magnetic resistance, Grand Seiko watches incorporate a two-layered dial structure, where a layer of pure iron is set underneath the dial. This two-layer construction was avoided with the SBGH255 to make certain that the watch was not too thick. SBGH255 still achieves a magnetic resistance of 16,000 a/m thanks to the specially designed pure iron dial.”
The SBGH255 was initially released in 2017, but due to the highly specific nature of the watch, it’s never been at the forefront of the conversation concerning Grand Seiko’s rise in recent years. Divers are typically associated with “core Seiko” and not Grand Seiko, but as a Seiko (and Grand Seiko) enthusiast it’s hard not to appreciate the outcome of unrestricted possibilities that a Grand Seiko diver presents. Sure, it has to follow the Grammar of Design, but the SBGH255 is what happens when we turn a standard Seiko diver up to 11 and pack it with the very best that Seiko Group has to offer. At $9,600 it’s not going to be the next Turtle, but it was never meant to be.
In my opinion, the SBGH255 is the baddest dive watch coming out of Japan, and it looks the part, too, with a case that’s 46.99mm wide and a height of 17mm. It’s large. But it’s important to understand that this is a “halo watch” that’s been engineered to push every spec to its limit and showcase Grand Seiko’s technical prowess when it comes to not just the zaratsu polishing on titanium (notoriously hard to work with), but also the hi-beat caliber 9S85 and a complicated case construction. It’s not a daily beater, but then again, neither is an Omega Ploprof, Rolex DeepSea, or Seiko Tuna.
There’s a huge gap in the level of execution between this and your average Seiko diver whether it be a discontinued SKX007 or a modern SRPD25 “Monster.” There are few apples-to-apples comparisons when it comes to the SBGH255, but I’d group it with the Ploprof, or perhaps the Sea-Dweller (even though they both have about twice the depth rating). They’re the most focused expressions of a dive watch from their respective makers and they’re engineered for wearability and functionality specifically in deep-sea environments.
While I wouldn’t be in a deep-sea environment, I was determined to at least get as close as possible to putting the SBG255 in an environment analogous to what it was designed for.
Florida is home to roughly 469,000 acres of mangrove swamp that can be found as far north as Cedar Key (due west of Ocala), and as far south as Key West. Jules Undersea Lodge is situated in a small mangrove lagoon on the coast of Key Largo, the longest of the Florida Keys.
Mangrove swamps are largely made up of evergreen trees that are salt-tolerant, and in the case of this specific lagoon, it was mostly “red” mangrove trees lining the nearshore tidal edge of Key Largo. The mangrove trees color the water a shade somewhere between rooibos tea and English Breakfast tea. In other words, it’s not in the picturesque aquamarine-hued water that’s usually associated with the Florida Keys. It’s brown and murky. And it only gets more brown and murky the deeper you go. We were warned that around the bottom, near the entry hatch to the habitat, there was a layer of colder water with a high concentration of suspended organic debris, drastically decreasing visibility.
Above, I’m demonstrating the ratcheting extension clasp. This is a 3.5mm wetsuit, and it easily accommodates it, plus my glove on top of that. That action is smooth, although sometimes during normal open-close operation, the diver’s extension will extend unintentionally.
Once we were briefed on the entry technique it was time to don the gear, including the watch, and make the trip down to the habitat. This would be the first open-water dive for my dive partner (and girlfriend). It went off without a hitch thanks to the expert guidance from Daniel Blezio, who works at Jules Undersea Lodge and mans the monitoring station overnight while guests stay in the habitat. He watches oxygen levels, the electrical systems, and pressure inside the habitat from a command station near the dock of the lagoon where Jules Undersea Lodge sits.
I lined up the bezel with the minute hand and emptied my BCD (Buoyancy Compensator Device) until I was neutrally buoyant and I could comfortably let go of the shot line. I wasn’t planning on using a significant amount of air or even logging much time during the descent, but I like to keep precise data for all the dives I do, no matter how short they are. And since this was a shallow and short dive, I left the computer back home. The SBGH255 was the only instrument I had to track the length of the dive. Along with the analog depth gauge, it was all I needed.
The video above depicts the descent down the shot line and the ingress process to the habitat.
We followed the shot line down, and as expected, a thick layer of suspended debris covered the bottom. The cloud surrounded the bottom quarter of the habitat, which almost looked like a skyscraper piercing the clouds when you’re climbing out of a city on a foggy day – except this structure was covered with barnacles. And the clouds were shades of mud.
By the time the habitat came fully into view, we’d already arrived. The visibility situation simply does not allow for a descent by sight alone. The shot line is necessary to help guide divers to the entrance hatch once you get into the murky stuff.
We surfaced inside the moon pool and I took note of the time that had elapsed. In at 14:38 and out at 14:45. It was short but exhilarating, and I was happy to see that everything went smoothly. Technically, it’s all considered one continuous dive, since the air inside the habitat is pressurized, so it’s like you’re breathing from your regulator even while you’re in the dry habitat. I kept thinking that it’s got to be a hell of a dive to experience your first time out of the pool. I don’t remember exactly what my girlfriend said after spitting out her regulator, but it was something along the lines of “Whoa. I did it.”
I checked to make sure my laptop and camera (used to shoot this story) had not suffered any leaks during the trip down; once that checked out I went on an excursion dive to check out the exterior of the habitat. A school of mangrove snapper was hanging out on the top of the habitat, and I peered inside the various ports built into the structure. It’s really impressive to think that humankind has learned to live and work in the ocean using these underwater habitats. Most of them were built in a totally analog era, and very little has been done to La Chalupa on a technical level over the course of its life, aside from maintenance and minor upgrades. The same technology that it debuted with in 1972 is still working today.
And on my wrist, the same L-gasket dive watch technology that Seiko first debuted in 1967 was working brilliantly, as well.
The only fish I can ID here is the mangrove snapper, very common in the Keys. They hang around the top of the habitat. I also tried to get some footage of the watch while swimming along the perimeter of the habitat.
Coming To Terms With The SBGH255
Grand Seiko is an entirely different company than Seiko now, at least in America. But in the case of the SBGHH255, there’s a strong link connecting the two companies that are desperately trying to put distance between themselves. Grand Seiko has no historical precedent when it comes to dive watches; that’s all Seiko. But getting into dive watches is very much a part of the playbook for the “new” Grand Seiko.
Back when Grand Seiko was a JDM-only affair, there were no significant divers in the range. So it only makes sense that Grand Seiko built on the legacy of Seiko when it comes to dive watches. Watchmaking technology and knowledge, as well as evaluation criteria specific to diver’s watches, are shared between the brands. To illustrate this notion, consider that the exact L-shaped gasket from Seiko’s SLA041 is used on the SBGH255. The complex curvature of the case follows the same pattern introduced with Seiko’s 6215 in 1967.
That’s what’s most interesting about Grand Seiko’s divers, and specifically the SBGH255. The line represents a chance for Grand Seiko to break away from the design precedent that was set by Seiko’s first professional divers (the 6215 and the 6159) and create a new visual language around the engineering technology that has been constantly perfected over the past 50+ years. The watch was designed by Shinichiro Kubo, who has since left the company. The design department is now headed by Kubo’s successor, Junichi Kamata. Kamata was able to shed some light on what makes the SBGH255 the bosu dive watch that it is.
Kamata noted that the case incorporates elements from some of Grand Seiko’s most notable models, saying it’s “inspired by the 44GS and 62GS and incorporates flat surfaces that shine powerfully and brilliantly on the wrist.”
I’ll admit, it’s entirely unfamiliar to wear a watch this big and serious that glimmers the way the SBGH255 does. It’s almost jarring how a tool watch has such a vibrant shine to it. Whenever I looked down at the watch I thought of the outsized “Buster Sword” that Cloud, from the popular video game series Final Fantasy, carries with him. Not only is the sword simply massive like the SBGH255, the lugs are reminiscent of the beveled edges and tanto design of his blade. In my opinion, the case is the watch’s most charming aspect. The case is made from seven pieces (less the crown, crystal, and gaskets) and features familiar lines all around, including the aforementioned 44GS and 62GS lines on the lugs, then the gorgeous curve of the 6159 (and all the designs it’s spawned) on the rear of the case. There’s simply no other diver quite like it.
There’s another unique element to Grand Seiko diver watches, and that’s the use of cathedral hands. Kamata explains that it’s not only for an elegant effect, there’s a practical purpose behind the unusual design. From Kamata:
All Grand Seiko diver’s watches share the same design layout. To develop this layout, we asked the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) to share with us real-life experiences of professional divers. What was most impressionable about their stories was how their cognitive abilities would impair when working in the deep sea, and how they could not read complex shapes in the deep. The best they can do is decipher the difference between circles, triangles, and squares. Therefore, we used those three shapes for the indexes and designed the layout to first and foremost make it easy to read the dial direction. At the same time, the most essential point when using a diver’s watch in the sea is the readability of the tip of the minute hand and the scales of the rotating bezel. For this reason, we placed a large triangle coated with LumiBrite at the end of the minute hand. LumiBrite shines the brightest when there is a lot of surface area. This is important because one naturally looks at where it shines the strongest when diving under the sea.
The latticework geometric pattern on the dial comes from a moment when the designer, Kubo, looked up while he was diving and observed the air bubbles exiting his regulator and traveling up towards the light. This image inspired the pattern on the dial.
Inside the massive case is the hi-beat 9S85; it ticks away at ten beats per second and makes the second hand sweep oh so smoothly, a real joy to observe when you’re done ogling the hairline polishing and bright mirror-like surfaces on the lugs. A lot of the cost is tied up in the movement, and normally I have a “git ‘er done” approach to calibers in dive watches. Give me something that doesn’t break and when it does it’s easy to fix, but the SBGH255 is an exception. There’s something special about having a movement inside a purpose-focused watch that’s among one of the most highly finished industrially produced examples out there, and that I know it’s meeting the advertised +5 to -3 seconds per day. The watch does wear smaller than the specs would suggest, and the titanium case makes it wear light and breezy on the wrist.
All told, the watch is an exercise in pushing the limits of a saturation diving-focused model the Grand Seiko way; it isn’t meant to wear like a Sub, or a SKX007 for that matter. I’m not certain that this watch was ever meant to be a commercial success, and that’s also why I’m so drawn to it. The size and materials are congruent with the role the SBGH255 is meant to play.
When thinking through the watch, I’d urge folks not to reduce their analysis down to “it’s too big for me” or “it’s too expensive.” A Boeing 747 is too big to park in my driveway and it’s way out of my budget, too, but I certainly still appreciate the queen of the skies for all that she is. And anybody who gets to fly one is privileged, indeed.
Life At Depth
There’s not a whole lot to do in a series of thick pressurized metal tubes anchored to the seafloor, but there’s more than you’d think. You can, for instance, watch a movie underwater. We took in the 1998 sci-fi thriller Sphere, based on Michael Crichton’s novel of the same name (years ago, I wrote about his watch). We also dined on hot pizza that was delivered fresh from the surface in a pelican case. I also read, almost in entirety, Living and Working in the Sea by Koblick and James W. Miller.
I thought about all the folks who had carried out important scientific research in this habitat, and about how they moved the needle forward. Also, about all the mistakes and learnings that were experienced as humans learned to live in the sea. Their work was the reason I felt safe and confident in the habitat.
Then my thoughts turned to the unfortunate truth that interest in manned undersea labs has waned in recent decades. I was a tourist in this habitat, with a sense of nostalgia for something that hadn’t even happened during my lifetime. I thought about the future of undersea living and how it doesn’t seem particularly bright. Mankind made so many advancements in undersea living during the ’60s and ’70s and then it just slowed down. What was once PRINUL is now a luxury hotel for tourists like me.
The creation of the Seiko saturation diving watch is a similar story. The L-shaped gasket and the associated technology that allows this SBGH255 to survive at 600m came from the work Seiko engineer Ikuo Tokunaga carried out for five years, starting in 1970, trying to create a watch that addressed the complex problems that arose from living and working at depth. That resulted in the Tuna, a cousin of the Grand Seiko SBGH255, which, after all these years, has become a luxury product.
But wearing the SBGH255, like staying in Jules Undersea Lodge, is the closest most folks will ever get to experiencing the life of an aquanaut and living and working in the sea. Life and tides both ebb and flow; maybe one day undersea living will be more accessible. And when that day comes, I know which watch I’ll be wearing.
For further reading on Jules Undersea Lodge and PRINUL, there really isn’t anything better than Living and Working in the Sea by Ian Koblick, the father of La Chalupa. It’s out of print and pricey, though. Underwater Studies in the Caribbean is a fantastic report, and it’s free! Finally, there is an organization that keeps the memory of PRINUL alive, it’s called PRINUL50 and some of the archival photos in this piece can be credited to this organization. They have an incredible selection of media to browse through.
For further reading on Seiko and Grand Seiko divers, Sadao Ryugo aka @mrseikosha on instagram is a fantastic resource. He’s the author of Seiko Diver’s Watch: The Birth Of Seiko Professional Diver’s Watch. I also would urge folks to read Jason Heaton’s piece on the development of Seiko saturation dive watches as well. It was updated in December ’21.
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The HODINKEE Shop is an authorized retailer of Grand Seiko. While we don’t currently carry the SBGH255, have a look at our collection, here.