The new Seiko Marinemaster Professional SLA081 is a hardcore, GS-powered monster tributing the very first Seiko diver
Borna BošnjakSeiko is a true watch fan’s watch brand, namely because there are so many important references, easter eggs, and Seiko Corp. sub-brands to keep track of, you’d have already become an enthusiast by the time you remember them all. Today, the topic is tributing the 60th anniversary of the very first Seiko dive watch from 1965 – the now-legendary 62MAS – but curiously, the headlining release for this celebration is referencing a watch from 1968 instead. I’m talking, of course, about the ref. 6159 with its hulking, monobloc case and high-beat movement that would eventually go on to inspire the Marinemaster line. The Seiko Marinemaster Professional SLA081 is the latest, and possibly greatest, member of that collection, sporting titanium monobloc construction, an innovative bezel retention system, 600 metres of water-resistance, and a Grand Seiko-derived movement. It might not look like the 62MAS, but it certainly feels like a worthy successor.
The case
Let’s start with that case, as it’ll be the defining feature of the SLA081. Getting the size out of the way first – it’s 45.4mm across, with a thickness of 16mm and lug-to-lug of 50.4mm. We often point out how the diameter is not the be-all-end-all of sizing, but in this case, it’s just as good an indication as any, as this is a proper beast on the wrist. There is a “but” here, and that’s the titanium case material. This watch is by no means lightweight, but I can’t imagine the heft if it was in steel.
The coolest part is undoubtedly the one-piece case construction, referencing the super-collectible ref. 6159 from the late ’60s and early ’70s. By removing a potential access point via the caseback, Seiko has to install the movement and dial from the front of the watch. You’ll also notice there’s no helium escape valve despite the SLA081 sporting 600 metres of water resistance, so how does it prevent the watch from exploding during decompression? Just like the titanium case material, here the SLA081 takes inspiration from yet another Seiko legend – the first-ever Tuna from 1975. Alongside the novel case material, the Tuna introduced a special L gasket that prevents helium from entering the watch in the first place.
You’ll also notice that the construction of the case does have an added complexity, with protruding black pieces between the lugs and under the bezel. That’s a special bezel-holding development of Seiko’s, allowing easier disassembly and cleaning simply by removing four screws on the caseback, rather than fitting the bezel directly to the case as usual.
And though it’s not a material Seiko often uses, the corporation’s expertise in titanium finishing is evident. The brushing and polishing is super well-done, with sharp transitions between the different facets most evident along the flanks of the case. It’s especially the polishing that draws the eye, as it manages to extract an impressive amount of lustre from a material that’s famously quite dull.
The dial
The dial is no less unique than the case, though it goes about it a bit more subtly. At first glance, it might appear a little odd that such an expensive watch would opt for simple pad-printing for its indices. The truth is a lot cooler than that. The Marinemaster SLA081 has indices that are actually part of the dial, as they’re pressed out into their convex shape from a single blank. As a result, the dials are better protected against shocks, as the indices could fall off, but still have a three-dimensional effect.
Seiko further emphasised the three-dimensionality by covering the whole dial in a thick layer of transparent lacquer that sits at the same height as the rehaut. As a result, the dial surface itself is flat, but the textured pattern below shifts and reflects like no dial I’ve seen before, helped by the gradient abyss blue finish. I know this is a watch made to meet the demands of deep-sea diving, but I could just as easily see this dial on a dressy Grand Seiko, it really is that good.
The bracelet
A common point of contention for many Seiko fans are their bracelets, which admittedly sometimes feel like a bit of an afterthought. Seiko has clearly taken notice, as their latest releases have all carefully considered this element of the watch, and the Marinemaster Professional SLA081 is no different. The multi-link, multi-finish bracelet is supremely comfortable thanks to its rounded links, and tapers down from the wide lugs so as not to feel overbearing.
The clasp is still quite bulky, though finished just as well as the rest of the bracelet, and offers diver’s extension functionality. It’s not as seamless as some tooless micro-adjusts out there, but it’s certainly utilitarian which is fitting for the rest of the watch.
The movement
Here I can’t even talk about being hidden behind a screw-down caseback, as there simply isn’t one, but Seiko still includes a medallion with its signature wave insignia. The 8L45 is new to the Seiko catalogue, also featuring in the new King Seiko VANAC line, and is derived from the Grand Seiko 9S65/9S68 line. It sports a 72-hour power reserve, upping it significantly from its 8L35/9S55 predecessor thanks to a thinner and longer mainspring, though unlike those original, high-beat Seiko Professional divers, it only beats at 4Hz.
The verdict
If you needed any more convincing, the SLA081 is also going to be field-tested as part of a Arctic research program by the Japan Agency for Marine-Earth Science and Technology (I can see why the JAMSTEC acronym is preferred). Seiko and JAMSTEC go way back, with numerous watches accompanying some proper deep dives, ranging from 600 metres in 1983 all the way down to 3,000 metres in 2014. Those 2014 Tuna references SBBN013 and SBDX011 were selected randomly from the production line and only rated to 1,000 metres, but survived all the way until 3,284 metres for the quartz, and an astonishing 4,299 metres for the automatic variant.
The Seiko Marinemaster SLA081 should be the complete antithesis of what I find cool in a watch personally – that being dinky, sub-38mm vintage pieces with questionable reliability – so the fact that I find it fascinating should say enough. The dial is phenomenal, and the case material and construction are a proper throwback to Seiko’s legends of the past without feeling overly gimmicky, and I needn’t say more about a Grand Seiko movement being used. With the SLA081’s proportions in mind, though, it would be easy to see it just overpower the appendages of us small-wristed folk, but with such an impressive spec sheet and those looks, I have a feeling the 600-piece limited edition is going to fly out of the display cabinets when it releases in July of 2025.
Seiko Prospex Marinemaster Professional 60th Anniversary SLA081 pricing and availability
The Seiko Prospex Marinemaster Professional SLA081 is a limited edition of 600 pieces, available in July 2025. Price: US$4,600, A$7,200
| Brand | Seiko |
| Model | Prospex Marinemaster Professional Seiko Diver’s Watch 60th Anniversary Limited Edition |
| Reference | SLA081 |
| Case Dimensions | 45.4mm (D) x 16mm (T) x 50.4mm (LTL) |
| Case material | Titanium and DLC stainless steel bezel insert |
| Water Resistance | 600 metres, screw-down crown |
| Crystal(s) | Sapphire front |
| Dial | Lacquered, textured grey-blue gradient |
| Bracelet and strap | Five-link titanium bracelet, folding security clasp |
| Movement | 8L45, in-house, automatic |
| Power Reserve | 72 hours |
| Functions | Hours, minutes, seconds, date |
| Availability | Limited to 600 pieces, July 2025 release date |
| Price | US$4,600 A$7,200 |