The Grand Seiko Spring Drive UFA Ushio 300 Diver, GS’ Smallest and Most Accurate Dive Watch

While dive watches are fundamental to Seiko’s Prospex collection, the concept is slightly less natural for Grand Seiko. At first sight… Indeed, the higher-end brand of Seiko Corporation has been active in the field of purpose-built diving instruments since 2008, delivering impressive models, whether in terms of specs, looks or, unfortunately, size. One of the main complaints heard over the years is that everything dive-oriented at GS was large and only meant for action, not so much for land-wearing and desk-diving. Grand Seiko has listened, and today delivers its most compact (and most precise) dive watches to date: a pair of reasonably sized yet fully equipped models that answer collectors’ requests. Here are the Grand Seiko Spring Drive UFA Ushio 300 Diver SLGB023 and SLGB025. 

Diving lineage at Grand Seiko

Surprisingly, it took Grand Seiko 48 years to enter the highly competitive dive watch market. Despite being born in 1960, the higher-end arm of the Seiko Corporation did not introduce its first dive watches until 2008, with the steel SBGA029 and titanium SBGA031, later renamed SBGA461 and SBGA463, featuring a GS-only signature on the dial (in 2021). Equipped with Spring Drive movements, these watches measured 44.2mm x 14mm. In 2014, Grand Seiko launched the SBGX115 and SBGX117, two 42.7mm quartz-powered models.

It took some more years for GS to deliver its first mechanical dive watches, the professionally-oriented 600m, titanium-clad references SBGH255 and SBGH257, both measuring close to 47mm in diameter, 17mm in thickness and equipped with hi-beat movements. Once again, watches that performed perfectly underwater, but not so much on land. In 2019, new quartz-powered models were presented, measuring 43.6mm in diameter, the references SBGX335, 337 and 339.

2020 marked the return of a high-end 600m professional diver, this time with a 46.9mm x 16mm titanium case, the reference SLGA001. This limited edition was notable for introducing a new generation of the Spring Drive movement: the calibre 9RA5, a slimmer, more powerful, more precise twin-barrel movement with a 5-day power reserve, which also found its way into the White Birch SLGA009. In 2021, Grand Seiko released a new pair of hi-beat mechanical dive watches, the SBGH289 (steel) and SBGH291 (titanium), with 200m water-resistant cases measuring 43.8mm.

Last, in 2022 and 2023 respectively, Grand Seiko released the SLGA015 and SLGA023 Ushio 200m Diver in titanium, the first dive watches in the Evolution 9 collection, equipped with the 5-day Spring Drive calibre 9RA5. Again, dimensions were far from compact, at 43.8mm x 13.8mm.

The reality with Grand Seiko dive watches

While Grand Seiko has been particularly strong in creating all-rounder, casually elegant watches over the last 10-15 years, with emblematic models such as the Snowflake or the White Birch, the same cannot be said about its dive watch collection. Why so? Well, there is intrinsically nothing wrong with GS’s dive watches. Most of them are well-performing diving instruments. But there are a few key elements that might have hindered their success. One, the design was probably too reminiscent of high-end Prospex models and not sufficiently differentiated. This might have created confusion, despite the two collections acting in different segments of the market.

Then, these watches never really hit the right spot in terms of water-resistance: 200m is seen by many as a bit too low for a luxury dive watch, while 600m is often overkill. Finally, the proportions of these watches might have made sense when worn over a diving suit, but far less when worn on a daily basis, where, let’s be real, most dive watches are being used. Apart from a few exceptions, not many can or want to run around town with a 47mm dive watch on the wrist. And finally, there was the recurring demand for a micro-adjustable clasp, an absence that was partially corrected last year with the release of the Spring Drive UFA SLGB003.

The Spring Drive UFA Ushio 300 Diver SLGB023 and SLGB025

Problem solved with the release of a new, smaller, thinner and yet highly capable series of dive watches by Grand Seiko. Part of the Evolution 9 collection and relying on the benefits of the compact Spring Drive UFA (Ultra Fine Accuracy) calibre presented last year on the Ice Forest SLGB001 & SLGB003 models, the Japanese luxury watchmaker is now able to release its most compact and most precise dive watches to date. And, even if a strong evolution is palpable with the new Ushio 300 Diver SLGB023 and SLGB025, the GS touch is still very much alive – maybe more than ever.

These new Spring Drive UFA Ushio 300 Divers are targeting the market for classic luxury divers, with the Rolex Submariner or the Omega SM300 Diver in mind. And that means a combination of robustness and refinement, Goldilocks dimensions and industry-standard water-resistance. All of that with GS identity. Let’s start with the case, which measures 40.8mm in diameter and 12.9mm in thickness, which is approximately the same size as a modern Submariner Date (40.5mm x 12.5mm). As you’d somehow expect from a Grand Seiko, the choice has been made to use High-Intensity titanium instead of stainless steel, a material known for its lightness (30% less than steel) and corrosion resistance – and, let’s be honest, it’s a classic GS feature that gives these watches a competitive advantage.

As for the shape, the Evolution 9 style has been clearly applied here, with a thinner profile, a more curved caseband, benefiting the balance on the wrist, a case that still relies on facets and sharp angles, but with more “flow” and “curves” than before (the case feels lighter, more ergonomic, more airy than before) and overall more attention to the detail. Here, the design language applied to the SLGA015 and SLGA023 as of 2022 has been transposed and reduced.

As for diving credentials, the Ushio 300 Diver SLGB023 and SLGB025 are not compromising here, with a 300m water-resistance, in line with the industry’s best-selling models, a screw-down crown partially recessed within lateral guards (but less than before for easier grip), a solid titanium back and, of course, a unidirectional bezel. Acting on 120 clicks, it features large notches, a ceramic insert in blue or green, and a fully graduated 60-minute diving scale. Only the small circle in the triangle is coated with lume. A fully-lumed scale would have been pleasant.

On the wrist, the evolution between the Ushio 300 Diver and previous models is undeniable. Even on my relatively small 16.5cm wrist, these two models wear comfortably and can easily be considered daily drivers or weekend watches. While they are capable dive watches, they are no longer relegated to this sole role and can be worn in town, too. As the owner of a modern Submariner, I find the overall wearing experience comparable, given the watch’s size, and, on top of that, the benefits of titanium and its lightness.

Moving to the dial, the Grand Seiko Ushio 300 Divers also bring their dose of evolution (9), particularly in the applied markers. Available in gradient blue (SLGB023) or gradient green (SLGB025), they are built on the same embossed pattern as the SLGA015 and SLGA023, a motif named ushio, meaning tide in Japanese. The use of a gradient effect has two benefits: it allows for a brighter, more saturated colour in the centre, adding more personality, while the darker edges create strong contrast between the background, the applied markers and the tips of the hands. A nice touch, Grand Seiko went for a no-date display, ensuring the presence of lumed markers all around (an ISO 6425 requirement) and offering a balanced display.

As said, the main evolution comes from the applied markers. In the past, all GS dive watches featured rather small, round hour markers, which might have missed the spot in terms of design consistency. Here, the new compact Ushio models have the prominent, rectangular indexes of the Evolution 9 Style. Faceted and diamond-polished on the edges, these offer more luminous surfaces and more consistency with the rest of the watch. The same can be said of the handset, which has been simplified, with the cathedral-like hour hand removed for a more modern look. The power reserve indicator, on the other hand, has been kept. It’s a bit of an oddity in this diving context, but also an element strongly rooted in the brand’s DNA. A bit like the left-side key on a 911…

Ultra-Precise UFA Calibre 9RB1

Under the hood is a new movement reference, the calibre 9RB1. It is essentially the same movement (calibre 9RB2) as introduced last year in the SLGB001 and SLGB003, later used in the SLGB005, but with the power reserve relocated to the dial rather than through the back (due to the closed caseback). This means we’re treated to the same benefits as the inaugural Ultra Fine Accuracy watches, with a compact, ultra-precise movement said to be the most accurate mainspring-powered wristwatch movement. Possible thanks to the Spring Drive technology, which merges the beauty and perpetuity of an automatic movement with the precision of a quartz regulating organ, the 9RB1 boasts an annual accuracy rate of ±20 seconds, or ±3 seconds per month. And that’s a worst-case scenario… This even finer accuracy is achieved thanks to new and enhanced manufacturing and processing methods for the three-month-aged quartz oscillator, as well as a newly designed IC. It also features a regulation switch that can be used during after-sales service to correct any accuracy deviations that may occur over long periods of use.

The movement itself is 30mm in diameter and 4.7mm thick, features 33 jewels and boasts up to 72 hours of power reserve. Even though invisible, the movement is decorated with the signature finishing of the Shinshu Watch Studio, with frosted plates and bridges bringing contrast to the polished bevelled edges.

A new bracelet and Micro-Adjust clasp

To be as thorough as possible, Grand Seiko also updates the bracelet of its dive watch, offering the Spring Drive UFA Ushio 300 Diver SLGB023 and SLGB025 a newly designed, fully brushed, 3-link High-Intensity titanium bracelet. The first and welcome evolution, specifically compared to other recent watches from the Evolution 9 collection, is a more pronounced tapering effect – the almost straight fall of the links in the White Birch and other equivalent models wasn’t to everyone’s taste.

Next is the clasp… Last year, Grand Seiko finally released its first micro-adjustable clasp with an on-the-fly mechanism allowing a multi-step comfort release. The system is back in the SLGB023 and SLGB025, but this time paired with another important dive-watch feature: a diving suit extension. The micro-adjustment system allows a 6mm extension in three steps, while the diving release adds another 18mm of length. The GS emblem on the clasp serves as a locking mechanism, preventing accidental release. And overall, the quality of the clasp is now totally on par with the rest of the watch, which was not necessarily the case in previous diving models, even recent ones.

Availability & Price

The Grand Seiko Spring Drive UFA Ushio 300 Diver SLGB023 and SLGB025 are, without a doubt, very welcome evolutions in the GS dive watch saga. More compact, more wearable, visually more pleasant and more consistent, yet still very capable, now featuring the right clasp and more precise than anything purely mechanical, these are fully equipped dive watches that are hard to fault, at least in objective terms. In short, serious contenders in the highly competitive market for 300m luxury dive watches.

As for the price, Grand Seiko will ask you EUR 12,500. It isn’t cheap on paper, specifically when compared to this new duo’s direct target, the Submariner Date, which retails for EUR 11,000 in black and EUR 11,550 in green. Then, the GS offers more in terms of technology, precision and materials. It’s also intrinsically a very different experience. Both models are released as part of the permanent collection and will be available from June 2026. The blue Ushio 300 Diver SLGB023 will be available from retailers, Master Shops and official boutiques, while the green SLGB025 is reserved for Master Shops and official boutiques.

For more details, please visit www.grand-seiko.com.