The Seiko Marine Master SLA023 Is A World-Class Diver

Seiko has built such a cult following and such success over the years that it’s easy to see why the company is able to offer so many great watches at great prices. Everything from unique dress watches to high-tech divers and chronographs can be found in the Seiko lineup, any one of which will make a solid companion. One, the SLA023, also known as the Marine Master or MM300, is an excellent example of what makes Seiko great.

The Seiko Marine Master diver features a solid movement, unique and precise case design, and a world-beating price. The $3,100 MSRP is almost a bargain for what you’re getting with the watch, and used it can be found or even less. Today’s post will dive a little deeper on the Marine Master to give you a detailed look at what makes it tick. 

Let’s get started.

The SLA023 features a deep blue dial, but other watches in the series can be had with a black or even green dial. Depending on the light, the dial and matching blue ceramic bezel shift colors from a deep blue to almost black and sunburst tones in between. It’s a mesmerizing effect that gives the Seiko an interesting look that draws the eye. The round hour markers and rectangular markings at six and nine o’clock stand out against the dark dial and the lume here is superb. Ceramic was an excellent choice for the bezel, not only for its upscale looks and legibility, but because it sets the Seiko on the same level as its heavy-hitting dive watch competition from Switzerland.

Seiko’s bracelets can be hit or miss at times, especially when we’re talking about the timepieces in lower price ranges. The good news about the SLA023’s hardware is that it’s a step up from the basic Seiko bracelet, both in finish and comfort. It’s given the company’s Diashield treatment, which helps it stand up to scratches and bumps, while its mix of polished and brushed elements give it an upscale look. There is still some hair-pulling that happens here, but once the watch is settled on the wrist it’s not a big problem. The bracelet also features a diver’s extension, which allows the wearer to tighten or loosen the clasp as their wrists expand and contract throughout the day.

Part of what helps the SLA023 achieve its 300M water resistance is its monobloc case. It’s hewn from a single piece of steel, which means there are no seams or entry points on the caseback. The crown, bezel, and dial are the only way for water to penetrate, but withstand the pressure with solid seals. The downside here is that servicing the watch requires the removal of the bezel and dial, but that’s not a worry for the casual wearer. 

Like many timepieces from Grand Seiko, the SLA023 features Zaratsu polishing on the case sides, which gives it a shiny, upscale look. Like the Marine Master’s bracelet, its case has been coated in Diashield, which can withstand quite a significant impacts and knocks without showing scratches. It’s the perfect mix of design and protection to make the watch both gorgeous to look at and tough for everyday use.

Under the hood, the SLA023 is powered by Seiko’s 8L35B automatic movement. It features a 50-hour power reserve and 26 jewels. It’s closely related to the Grand Seiko 9S55 movement but lacks the regulation of its upper-crust counterpart. Still, the movement achieves the accuracy and durability needed to make the SLA023 a daily wear, and unless you’re a stickler for tracking seconds throughout the day you’ll never notice the difference. 

This is a gorgeous watch, and is one that carries features and tech that far outweigh its price tag. It’s a solid alternative to legendary divers like the Omega Seamaster and Rolex Submariner, but it should also be said that the Seiko Marine Master is one hefty piece of kit. With a case diameter over 44mm and a thickness of 15.4mm, the watch isn’t for all wrists, and with the bracelet it can be quite heavy. That’s its biggest weakness, but can also be its big selling point for many buyers.