Grand Seiko Spring Drive UFA Ushio 300 Diver Watch Review
The new Grand Seiko Spring Drive UFA Ushio 300 Diver has just been unveiled at Watches & Wonders 2026. Offered in a choice of two, tide-themed dial executions, blue (SLGB023) and green (SLGB025), the watch illustrates the Japanese company’s unwavering pursuit of continuous improvement. Angus Davies explores the composition of this latest divers’ watch in detail.
Grand Seiko – accurate, legible and beautiful
Ever since the first Grand Seiko timepiece burst onto the watch scene in 1960, the luxury marque has pursued its own path to greatness. The inaugural model was blessed with clean, uncluttered lines that conferred notable elegance, while the Dauphine-style hour and minute hands elegantly enunciated the prevailing time. ‘Accurate, legible and beautiful’ have remained defining characteristics of all timepieces bearing the GS name.
The inaugural model of 1960 was equipped with the Calibre 3180, a hand-wound movement, while the dial bore the word ‘chronometer’ presented in cursive text. From the outset, the die was cast, all Grand Seiko watches would forever be known for delivering impressive chronometric performance. The Calibre 3180 had a stated accuracy of +12 to -3 seconds per day, impressive numbers at the time. Since then and in a spirit of continuous improvement, the Japanese company has embraced new designs and cutting-edge technology in its quest to deliver superior precision.
Rather than fixate on one means of controlling the flow of time, Grand Seiko has embraced quartz, mechanical and Spring Drive movements. While each approach takes a different route to powering indications, all calibres have delivered impressive precision. Moreover, instead of resting on its laurels, the luxury brand has continuously sought advancement, not only in terms of improved accuracy, but also enhanced shock resistance and autonomy, where appropriate.
Grand Seiko Spring Drive (2004)
Grand Seiko is characterised by the tenacity of its employees. In the 1970s, an engineer working for Seiko Epson harboured a dream of creating a timepiece that had the precision of a quartz watch but powered by a mainspring. This engineer, Yoshikazu Akahane, would dedicate the next 20 years of his life developing what is now known as ‘Spring Drive’. Eventually, in 2004, the company unveiled the inaugural Grand Seiko watch fitted with a Spring Drive movement (Calibre 9R).
What is Spring Drive?
A conventional mechanical watch features a mainspring within a barrel, storing energy for future use. The mainspring is tensioned by winding the crown manually or automatically using an oscillating mass, harvesting energy from the natural motion of the wearer’s wrist. With an abundance of energy stored within the barrel (the fuel tank of the watch), the mainspring will seek to return to a relaxed state. Therefore, the release of the energy must be controlled by using a series of gears (gear train), ultimately serving the escapement with an impulse, causing the balance to swing back and forth (like a pendulum in a grandfather clock). After the balance wheel is pushed, the escapement momentarily unlocks, allowing the gear train to advance a set amount before locking again. The period between the locking and unlocking phases are controlled by the balance wheel oscillating to and fro, controlling the flow of time.
Spring Drive, a proprietary technology, employs a mainspring just like a mechanical watch. Some of the torque from the mainspring is diverted to a ‘Tri-Synchro Regulator’, converting mechanical power into electrical power which, in turn, is used to excite a quartz oscillator, which has a frequency of 32,768 Hz. Thereafter, the quartz oscillator provides a reference signal to an IC (integrated circuit). The remaining power from the mainspring is sent via a gear train to the glide wheel. Unlike a balance wheel in a mechanical watch, the glide wheel is unidirectional and its rotational speed is governed by the IC and an electromagnetic brake.
A notable benefit of a Spring Drive movement is that it delivers a level of accuracy unmatched by a mechanical movement fitted with a Swiss lever escapement. Incidentally, one trait of a Spring Drive movement is that the central seconds hand doesn’t tick, instead it glides. This characteristic is beloved by legions of GS devotees.
Grand Seiko Spring Drive UFA Ushio 300 Diver – Calibre 9RB1
Last year, at the Genevan fair, the Japanese marque unveiled the Grand Seiko SLBG003 Spring Drive UFA. This watch is fitted with the Calibre 9RB2, the first movement to bear the ‘UFA designation’ (Ultra Fine Accuracy), accurate to ± 20 seconds per year.
Now, at Watches & Wonders 2026, Grand Seiko has just unveiled a new divers’ watch, the Spring Drive UFA Ushio 300 Diver. This watch is equipped with a new movement, the Calibre 9RB1 and, once again, is accurate to ± 20 seconds per year. The brand attributes this impressive level of precision to ‘vacuum sealing the crystal oscillator, which has been stabilised through a three-month aging process’ and coupled with the IC, minimises the influence of external factors such as temperature, humidity, static electricity and light. ‘Each oscillator’s frequency is measured at multiple temperatures, and the resulting data is programmed into the low-power IC to enable precise thermo-compensation. The movement features a regulation switch that can be used during after-sales service to correct any divergences in accuracy that may occur over long periods of use.’
With a conventional mechanical calibre, as the mainspring relaxes, the force serving the escapement reduces, influencing the rate of the movement. In the case of the Calibre 9RB1, the mainspring still relaxes, but the combination of the IC and electromagnetic brake ensures the rotational speed of the glide wheel remains unaffected, thereby conferring rate stability. The Calibre 9RB1 has a power-reserve of 72 hours.
Grand Seiko Spring Drive UFA Ushio 300 Diver – inspiration and heritage
GS obsessives, of which I am one, will be aware of the brand’s fondness for artisanal crafts, Japanese history and nature. Indeed, the company has crafted dials inspired by snow, mountains, trees, rivers and cherry blossom. In this instance, the new watch is endued with an Ushio dial, a ‘tide’ themed design, first introduced in 2022 with the release of the Ushio Tide Spring Drive SLGA015.
There is a long tradition of Ama (Japanese ‘sea women’) diving for abalone, sea urchins, seaweed and pearls. Wearing traditional masks, fins and weights, the Ama free-dive to depths of 20 metres, holding their breaths for up to 2 minutes, their physiology and skill making them ideally suited to the task. Similarly, Seiko and Grand Seiko have an impressive track record inhabiting the subaquatic world, crafting watches designed to operate within the darkest depths of a cetacean blue ocean. In fact, Seiko has even attached prototype watches to the exteriors of submarines, subjecting them to the colossal forces experienced at great depths. Divers’ watches are part of Grand Seiko’s DNA and it is the brand’s knowledge of this horological genre that has influenced the design and construction of its models.
Grand Seiko Spring Drive UFA Ushio 300 Diver – dial
The dial of the Spring Drive UFA Ushio 300 Diver perpetuates the company’s reputation for peerless legibility. It subscribes to the brand’s ‘Evolution 9 Style’, a design language that was introduced in 2020.
Grand Seiko offers the Spring Drive UFA Ushio 300 Diver in two versions: a blue dial (SLGB023) and a green dial (SLGB025). Both dials feature a textured epidermis, the former hue replicating the appearance of ‘light streaming into a deep ocean’, while the green dial ‘draws from the tranquil beauty of shallow coastal waters near the shore’.
The hour and minute hands are fulsome and lined with expanses of white ‘Lumibrite’, bestowing a green emission in restricted light. Close examination of these hands reveals they sport a brushed finish on their upper surface; the minute hand has a prominent triangular tip, while the end of the hour hand is truncated. Each hour is denoted with a plump, rectangular index featuring faceted edges and incorporating a generous helping of Lumibrite. The central sweep seconds hand advances with a smooth, serene gait, courtesy of the watch’s Spring Drive movement, and is fitted with a circular luminescent counterweight, aiding readability.
Returning to Watches & Wonders 2025 and the release of the Grand Seiko SLGB003 Spring Drive UFA, its movement, the Calibre 9RB2, featured a power-reserve on its exterior, visible through an exhibition caseback. The new Spring Drive UFA Ushio 300 Diver stays true to divers’ watch convention by having a solid caseback, hence Grand Seiko has placed the power-reserve indicator on the dial, positioned at 8 o’clock, succinctly conveying the status of the mainspring. A minute track, presented on a flange, fringes the dial and, once again, proves effortless to read, both in daylight and in the dark. Beyond such practical considerations, the dial proves eminently handsome.
Grand Seiko Spring Drive UFA Ushio 300 Diver – case
In recent years, titanium has become an increasingly popular material for watch cases. Light, corrosion resistant and hypoallergenic, the metal has much to recommend it. In Europe, both Swiss and German brands use either Grade 2 or Grade 5 titanium.
Grade 2 titanium is virtually pure (≥ 99% titanium). It has ‘excellent cold-formability and ductility’ making it suitable for precision stamping. The metal exhibits a silvery-white or grey hue and is often endowed with a matt texture.
Grade 5 titanium is an alloy comprising approximately 6% aluminium, 90% titanium and 4% vanadium. The alloy also contains small traces of iron and oxygen. This material is much stronger than Grade 2 titanium and it can be polished to a resplendent gleam. Unfortunately, due to its hardness, the material cannot be stamped, hence it must be shaped using a CNC (Computer Numerical Control) machine, a far costlier method of production.
The case of the new Spring Drive UFA Ushio 300 Diver is made of a ‘High-intensity titanium’, a proprietary alloy that is said to be ‘twice as hard as steel’ (stainless steel) and yet 30% lighter. The brand does not reveal the precise composition of its alloy, but like Grade 5 titanium it can be polished to a high gleam. Grand Seiko fully exploits this latter characteristic with its legendary Zaratsu polishing technique.
Zaratsu polishing involves securing the case within a special holder, before the artisan presses it against a rotating, abrasive disc. The shape is refined, culminating in a remarkably smooth surface. Thereafter, the case is burnished to a mirror-like gleam, resulting in a distortion-free appearance, where reflections are faithfully replicated without any signs of twisting or warping.
It is this faithful depiction of light that is another GS trademark. In Japanese culture, the juxtaposition of ‘light and shadow’ is highly prized. In this instance, polished and ‘hairline finishes’ sit in harmony, imbuing the watch housing with a nuanced aesthetic.
Beyond its aesthetic charms, the ergonomics of the multi-faceted case have been optimised which, in combination with the low mass of the watch, confers superb wearer comfort. Another feature that contributes to the pampering wrist fit is the new ‘ultra-slim’ bracelet which is equipped with ‘a newly developed locking extension clasp with micro-adjustment’. This allows for up to 6 mm of adjustment, while the extension, used when wearing a wetsuit, can be extended an additional 18 mm.
The bezel incorporates a ceramic insert, a material that is virtually scratch resistant, corrosion resistant and won’t fade with the onset of years. The unidirectional, ‘120-click bezel’ features a count-up scale and incorporates a luminescent pip at noon.
As stated earlier, I am a GS fan and owner. I possess a first generation, stainless steel SBGA029 and it will forever remain a prized possession. Measuring 44.2 mm in diameter, the scale of the watch looks at ease on my larger-than-average wrist (19 cm circumference). However, I concede that for some would-be wearers the model may prove too large. With the advent of the new Spring Drive UFA Ushio 300 Diver, Grand Seiko delivers a watch that is neater, measuring 40.8 mm in diameter with a case thickness of 12.9 mm. For most would-be wearers, these dimensions will prove ideal.
And before you begin to wonder, the water-resistance hasn’t been dumbed down in order to shrink the new model’s overall dimensions. On the contrary, the new Spring Drive UFA Ushio 300 Diver, as its name implies, is water-resistant to 300 m or 50% more than my SBGA029.
Closing remarks
When a product proves popular, there is a temptation for a company to sit on its hands and simply watch the cash roll-in. However, standing still is clearly anathema to Grand Seiko, a brand that has continuously pursued product advancement. Objectively, the Spring Drive UFA Ushio 300 Diver is lighter than my beloved SBGA029. Furthermore, the high-intensity case is harder, the watch is neater, the bracelet offers more adjustability and the movement delivers superior precision. All these attributes make a compelling argument for acquisition. However, I would never part with my SBGA029 in favour of a younger model. Indeed, it is my belief that you never sell a Grand Seiko you merely grow old together.
Further reading
https://www.grandseikoboutique.co.uk/
Technical specification
- Model: Grand Seiko Spring Drive UFA Ushio 300 Diver
- Reference: blue dial (SLGB023)
- Reference: green dial (SLGB025)
- Case: high-intensity titanium, diameter 40.8 mm, height 12.9 mm, water resistance 30 ATM (300 m), sapphire crystal to the front and solid screw caseback
- Functions: hours, minutes, centre seconds, power-reserve indicator
- Movement: Calibre 9RB1, automatic movement, Spring Drive, power reserve 72 hours
- Bracelet: High-Intensity Titanium bracelet and folding clasp with push button release, locking extension clasp and micro-adjustment feature
- Price: £10,500 (RRP as of 14.4.2026)