The bold new Seiko Prospex Marinemaster Professional Titanium SLA081

In 1965, Seiko entered the race for the best dive watch, much later than the Swiss did. Seiko released its first ever dive watch, known as the 62MAS, the mother of all upcoming aquatic watches of the brand. It’s a story that we’ve told many times on MONOCHROME. What matters most today is that 2025 marks the 60th anniversary of this historically important watch. As you’d expect, Seiko will be celebrating by releasing several new watches. And without further ado, let’s get straight to the star of the show, a bold, ultra-technical watch that’s part of the Marinemaster collection, which relies on a design modelled after a 1968 watch and that uses technologies created back in 1975 – dates that will speak to the fans of the brand. Let’s talk about the new Prospex Marinemaster Professional Titanium SLA081 – the new king of dive watches at Seiko. 

1965, the first Seiko diver, the 62MAS

The first… Just because of that, the Seiko 62MAS is a watch of great importance. Back in 1965, when it was presented, it was both Seiko’s and Japan’s first purpose-built dive watch. It took about 12 years for Seiko to react to the invasion of Swiss-made dive watches – which started in 1953 with Blancpain, Zodiac and Rolex. Nevertheless, the Seiko 62MAS has to be considered the mother of all upcoming aquatic watches of the brand. Fonts, dial colour, bezel style, case style, it’s all there… Many of Seiko’s modern dive watches are still deeply inspired by this reference 6217.

The Seiko 6217-8000/1, nicknamed 62MAS, had strong arguments: an automatic movement (calibre 6217A), a 150m water resistance, a large (at that time) 38mm case with a mono-bloc shape (rather massive integrated lugs, which guarantee the solidity of the case) for maximum protection and a dark grey dial with large indexes and hands, of course, all luminous. The bezel was already featuring a perfectly readable 60-minute insert, with all the required markings, but was still bi-directional. But what matters most is how influential this watch has been on both future releases of Seiko and the dive watch industry in general – remember that Seiko had played an important role in the definition of the ISO 6425 standard for dive watches. And this watch is now celebrating its 60th anniversary.

The Marinemaster Professional Titanium SLA081

What we’re looking at here is a beast… A true professional dive watch made for saturation diving, with huge dimensions, equipped with everything Seiko had under its sleeve, and priced at a point where it could almost become a Grand Seiko (in a way, it shares some technical similarities…) Yes, the SLA081 is the new reference dive watch of Seiko, and the brand wants you to know it.

So what has Seiko done to make this Prospex Marinemaster Professional better than the rest of its dive watches? Basically, the brand has sourced the design from its 1968 Hi-Beat 300m Diver 6159-7001, which was later recreated with the SLA025 and modernised it with multiple technical elements borrowed from another important watch, the 1975 Tuna Can. The new SLA081 is a large, professional-oriented dive watch that measures no less than 45.3mm in diameter and 16mm in thickness. To compensate for these bulky measurements, the brand has made it in lightweight titanium with super-hard coating. The overall shape is, without a doubt, a classic of the brand, with large shoulders, a crown at 4 o’clock and a raised bezel that has deep notches for an easy grip.

Contrary to most other watches by Seiko, this new Marinemaster Professional Titanium SLA081 relies on a fairly complex construction, and not a classic 3-part case. It actually uses a one-piece titanium case design that ensures water resistance to depths of 600 meters, suitable for saturation diving. There’s no caseback per se, and the movement is encased from the top. Also, just like Seiko’s historic Tuna watch introduced in 1975, it features a specially developed L-shaped gasket to prevent helium infiltration, eliminating the need for an escape valve. Finally, there are black-coated elements between each lug, which are secured by the back with screws, and that hold the whole watch and bezel together to ensure its resistance to pressure.

As a proper dive watch, there’s of course a unidirectional bezel. The stainless steel bezel insert, with a classic 60-minute diving scale, has been treated with diamond-like carbon (DLC) coating that ensures a hardness six times greater than it would otherwise be, making it more resistance to scratches – that being said, I don’t understand why such a high-end watch doesn’t come with a ceramic bezel.

The dial of this SLA081 is inspired by the deep sea, with an embossed wave pattern that’s been coated with a thick, clear lacquer that adds to the depth of the dial. It uses a gradient blue effect that deepens toward the outer edge, and while the texture is surely present and fairly captivating, it is not disturbing and keeps the watch highly legible and contrasted. The markers are not applied but formed as part of the dial through a molding process, as Seiko mentions that this method ensures that the hour indexes will stay firmly in place even under great impact. The latter, as well as the large faceted hands, are largely coated with LumiBrite, and this Marinemaster Professional Titanium retains a more balanced date at 3 o’clock (not at 4h30), while also having a small luminous marker next to it.

Inside the case of the titanium Marinemaster SLA081 is the calibre 8L45, a new movement that’s never been used in the past. It doesn’t share its specs or jewel count with the calibre 8L35, normally used in high-end Seiko dive watches. This movement, with 35 jewels, measures 28.4mm in diameter and 6mm in thickness and is actually derived from the Grand Seiko Calibre 9S65 (same jewel count, same dimensions, same 72h power reserve). It operates at 4Hz and has a claimed accuracy here of -5/+10 seconds/day.

As you’d expect from a pro dive watch, the Prospex Marinemaster Professional SLA081 comes with a metal bracelet, also made in titanium with uper-hard coating. It features rounded links designed to provide a flexible and comfortable fit. It is closed by a complex clasp with a push-button release, a secure lock, and a slide adjuster to extend it when worn over a diving suit.

A limited edition of 600 pieces available from July 2025, the Seiko Prospex Marinemaster Professional 60th Anniversary SLA081 will be priced at EUR 5,200. For more details, please visit seikowatches.com.