You’d be forgiven if dive watches weren’t the first thing that came to mind when thinking of Grand Seiko. The Japanese luxury brand makes some of the finest (if not the finest) dress watches on the planet, so the idea of them going full rugged for underwater exploration might seem off-center.
Nevertheless, the watchmaker has had divers in its catalog since 2008, but it was its Evolution 9 models that debuted in 2022 where we could really see what Grand Seiko was capable of. With the introduction of the Spring Drive U.F.A. (Ultra Fine Accuracy) last year, the Evolution 9 divers are also getting revised, but not just mechanically. These watches are more wearable as well.
A Long Time Coming
For a brand that debuted in 1960 and spent its first few decades perfecting the dress watch, diving was never really in Grand Seiko’s DNA the way it was for former-parent Seiko, whose 62MAS from 1965 is essentially the grandfather of Japanese dive watches.
While Grand Seiko’s early Spring Drive divers were technically impressive, they measured a hulking 44.2mm by 14mm. Follow-up iterations through the 2010s and 2020s pushed water resistance up to 600m in some cases, but never really cracked the proportions problem. The 2022 Ushio divers (SLGA015 and SLGA023) brought the Evolution 9 design language to the underwater lineup, but at 43.8mm by 13.8mm with only 200m of water resistance, they were far from the most practical dive watches on the market, let alone the most capable.
That all changes with the new Spring Drive U.F.A. Ushio 300 Diver.
Getting the Size Right
Fans rejoice as the new SLGB023 and SLGB025 clock in at just 40.8mm in diameter and 12.9mm thick, yet provide the wearer with a solid 300m of water resistance. For context, the proportions are basically the same footprint as a Rolex Submariner Date. The case and bracelet are both built from Grand Seiko’s proprietary High-Intensity Titanium, which runs about 30% lighter than stainless steel without sacrificing any scratch resistance.
To increase the water resistance, the crown is screw-down and partially recessed behind lateral guards. Meanwhile, the unidirectional bezel operates on 120 clicks with a ceramic insert.
The bracelet itself is newly designed with a tapered three-link layout and a locking extension clasp that covers 6mm of micro-adjustment in three steps, plus an additional 18mm for diving suit use. We personally love the GS emblem on the clasp, which serves as the lock.
Dial Talk
It’s not a Grand Seiko watch without having a beautiful dial, and the new diver certainly follows suit. The Ushio dial pattern, a wave-textured motif that’s been part of the Evolution 9 diver lineup since 2022, returns here in gradient blue (SLGB023) and gradient green (SLGB025). The blue goes deep-ocean dark at the edges, while the green references shallow coastal water. The color gradience towards the center creates solid contrast with the applied indices and hands.
Speaking of the indices, they’ve been upgraded to the bolder rectangular markers of the Evolution 9 Style with diamond-cut edges and Lumibrite fill. This replaces the rounder hour markers that looked a bit soft on earlier GS divers and is a more cohesive look all around.
Instead of a date window, the power reserve indicator, a longtime Grand Seiko signature, makes its way onto the dial face here since the caseback is solid on this reference. Not everyone will love this on a diver, but it’s definitely on-brand for them.
An Impressive Movement
The Caliber 9RB1 is a variant of the U.F.A. movement that debuted last year in the SLGB001 and SLGB003. It’s a 30mm x 4.7mm Spring Drive with a 72-hour power reserve and holding the distinction of being the most accurate mainspring-powered wristwatch movement in existence right now. That ±20 seconds per year rating (roughly ±3 seconds per month) is achieved by vacuum-sealing a three-month-aged quartz crystal oscillator with the IC, then programming each oscillator’s frequency data across multiple temperatures for precise thermo-compensation. Hand-assembled at Grand Seiko’s Shinshu Watch Studio in Nagano Prefecture, it also features a regulation switch for accuracy correction during servicing. There’s simply nothing else like it.
Spec Sheet
Model: Spring Drive U.F.A. Ushio 300 Diver
References: SLGB023 (blue), SLGB025 (green)
Case Material: High-Intensity Titanium
Case Diameter: 40.8mm
Case Thickness: 12.9mm
Movement: In-house Caliber 9RB1 Spring Drive U.F.A.
Accuracy: ±20 seconds per year (±3 seconds per month)
Power Reserve: 72 hours
Water Resistance: 300m
Crystal: Sapphire with inner anti-reflective coating
Lume: Lumibrite
Bracelet: High-Intensity Titanium, three-link, locking extension clasp with micro-adjustment
Pricing & Availability
The Grand Seiko Spring Drive U.F.A. Ushio 300 Diver is priced at $12,400 for both references and hits Grand Seiko boutiques and select retail partners in June. The blue SLGB023 will be available through authorized retailers as well, while the green SLGB025 is exclusive to Master Shops and official boutiques.
Recap
Grand Seiko Spring Drive UFA Ushio 300 Diver
Grand Seiko’s new Ushio 300 Diver is the brand’s best dive watch yet, finally hitting the right proportions at 40.8mm while packing in the world’s most accurate mainspring-powered movement.
