Two For Tuesday: Seiko Marinemaster 300 Vs. Baby Marinemaster

It’s Two For Tuesday time and this week we take a look at the Seiko Marinemaster 300 versus the so-called Baby Marinemaster. Let’s see if a mere 100 meters is all that separates these two (marine)masters of the deep.

Before we get to the Marinemaster and its stable mate, let’s talk Omega. Specifically, I asked you to consider the iconic Speedmaster Professional against the far newer Seamaster 300M. It seems that practicality trumps the moon because the modern diver took home a solid 53% win. We thank the nearly 3,000 of you who voted and the many who commented. The comments, by the way, were almost all in support of the 300M and its everyday abilities. Today, we’ll look at two watches of the same ilk and ask you to make a choice.

Seiko and its slew of divers

Within its Prospex series, Seiko now offers a dizzying array of dive watches. I suppose that they always did, but they weren’t always available around the world. Case in point, the legendary Marinemaster 300 was kind of a grey market special for much of its early life as the SBDX001. Sure, there were importers, but that was a little dodgy. Then, Seiko began to expand during the time of the short-lived SBDX017 Marinemaster 300 and it was sold globally. We applauded these watches due to their incredible value for money proposition. Fans labeled them as giant-killers due to big specs and pricing often well below €2,000. Then things changed.

Moving upmarket with the Marinemaster and Prospex

Within the last few years, Seiko has made the decision to move in a decidedly upmarket direction. Yes, cheap Seiko tool watches are still out there, but it’s believed that you’re choosing from the last dregs of old stock. Going forward, it seems that the price of entry for a mechanical Prospex diver will begin in the €400 range. And what of our beloved Marinemaster 300? As we’ll see, it still offers a lot of bang for the buck (or Euro), but you’d better bring over 3,000 of them to the party to gain entrance.

Seiko didn’t forget about those who covet value and specs in the €1,000 range. The brand offers loads of choices in this popular segment. In particular, this is where the famous Sumo holds court. But it’s also where Seiko likes to market its “modern reinterpretation” dive watches such as the 62MAS, 6105 “Willard”, and the 6159. It’s this latter model where we’ll hover and take aim with our trusty speargun. You’ll see why in a bit, but the fact that the 6159 modern reinterpretation has gained the nickname “Baby Marinemaster” should give you a clue. This watch has become a common foil to the once no-brainer choice of the Marinemaster 300.

The Seiko Marinemaster 300

Let’s clear this up straight right out of the gate. The current 300-meter Prospex dive watches from Seiko no longer use the “Marinemaster” name. Actually, the name isn’t used anywhere within Seiko any longer. That still hasn’t stopped fans from using the term, though, because today’s Professional diver is clearly an evolution of the famous MM300. It was only back in 2018 that Seiko quietly transitioned from the aforementioned SBDX017 to a modernized version of the Marinemaster 300. They made this move in true Seiko fashion with nothing less than a limited edition.

The SLA019 kicked off things for the new Marinemaster 300 and I happened to buy one. I’d never bought an SBDX001 or SBDX017 and thought I’d join the club with a lovely green model that I lined up in a comparison article with the equally green Rolex Submariner Hulk. In any case, at that time, Seiko hadn’t really let on that the SLA019 was the beginning of a new breed of Marinemaster 300s. Now, we know it to be the case.

Upgraded specs

The newest Marinemaster 300 Professional diver differs from its predecessors with some high-class touches. Seiko finally added a sapphire crystal in lieu of its homegrown Hardlex mineral glass. This was a gimme and something the fans had requested for ages. Similarly, the dive bezel moved to ceramic and became a little larger and table-flat. Little dial changes were introduced primarily related to added or deleted verbiage. The extra hard coating Seiko calls DiaShield helps ward off scratches to the case. The case remained a front loader and comes in at 44.3mm in diameter (50mm lug to lug) and 15.4mm in thickness. The lugs are cross-drilled which makes swapping the included stainless bracelet and silicone straps a breeze.

Variety comes at a price

Since the introduction of the limited SLA019, we’ve gained some regular production models and another limited edition. The SLA023 is dark blue and the SLA021 is black (RJ reviewed that one last year). Both retail for €3,200. There’s also the limited edition (600 pieces) black-cased SLA035 for €3,000, but it’s only on rubber.

Despite improved specs, the fact that the Marinemaster 300 now retails for over €3,000 has actually caused it to lose a step. The reality is that this is no longer a “bargain” or quite the giant killer that it once was. 3K is serious dinero and also opens the door to a lot of other watches new and used from some pretty big names. That being said, this watch still contains the fantastic in-house caliber 8L35 automatic and that’s essentially an undecorated Grand Seiko movement. It runs at -10 to +15 seconds per day which doesn’t sound so hot, but owners consistently report better. A 50-hour power reserve allows for a weekend-long rest.

A couple of concerns

My beef with the Marinemaster 300 lies in two distinct areas. First, there’s no denying that this watch is one tall and chunky nugget. Whoever wears and owns this watch needs to possess large wrists or has to get used to a towering presence. Plus, it makes every day wearing challenging unless you normally sport short-sleeved shirts. Then there’s the bracelet. As good as the silicone rubber strap has become, this bracelet still lags the competition. I’ve always found the styling fussy and the clasp, while functional, looks cheap. There’s a lot of stamping there that doesn’t scream “3,000 EUROS”! I wear mine every so often, but nowhere near as often as I do other divers with similar capabilities.

Still, though, the Marinemaster 300 is a spec beast, and, if anything, it might shine a light on just how cheap preceding models were. After all, where also can you get a fully in-house mechanical saturation diver for this price? And let’s not forget that the watch is well made and rocks a very clean, functional design with ridiculous lume. But let’s bring up what has perhaps become the Marinemaster 300’s biggest problem and that’s the Baby Marinemaster.

The Baby Marinemaster

2018 was the year of the diver for Seiko. Aside from the SLA019 that debuted, Seiko brought us a limited edition reissue of its 1968 Hi-Beat 300-meter diver. And, true to form, the brand brought serial production modern re-interpretations of the 6159. References SPB077 (black on bracelet) and SPB079 (blue on rubber) were introduced and thus was born the “Baby Marinemaster”.

The Baby Marinemaster brought a 44mm stainless case (51mm lug to lug) with 200 meters of water resistance. Like the Marinemaster 300, its case features a DiaShield hard coating and a sapphire crystal. The bezel makes do with a high gloss painted material that we’re guessing is aluminum underneath. The mid-grade 6R15 brings 50 hours of power reserve along with -15 to +25 seconds of accuracy per day. Most importantly, this series of watches comes in at a skinny minny 13.1mm in thickness.

Loads of Baby Marinemaster variants

Since 2018, we’ve also seen a non-stop parade of new colors and limited edition models added to the Baby Marinemaster collection. Today we have the dark green SPB105 on a bracelet for €1,100, the PADI edition SPB087 on a rubber strap for €900, the blue SPB083 on bracelet/rubber for €1,200, the black SPB077 on the bracelet for €1,050 and the black with blue bezel SPB079 on a rubber band for €900. Whew! And that doesn’t even include the green SBDC079 “Ginza Edition” that I was fortunate enough to grab last year — there were only 300 of these JDM models.

Admittedly, the Baby Marinemaster didn’t immediately catch on with fans. With its arrow and sword hour and minute hands, a lot of people dismissed it. No, this modern style of hands hasn’t been met with universal praise by longtime fans. However, once these watches hit Seiko’s growing number of boutiques, the magic began to unfold. People tried them on and realized that this just might be the sweetest diver in the Seiko lineup.

A huge difference in thickness

I head back to that 13.1mm thickness and the 2.3mm difference between it and the Marinemaster 300 becomes readily apparent. The Baby Marinemaster feels like a normal watch and that’s actually something we’ve missed in a middle range Seiko diver for a long time. Plus, the Oyster-esque bracelet is a real winner. It’s nowhere near Rolex good, but it’s actually better than the MM300’s hardware! It has an external wetsuit extension adjacent to the clasp that’s admittedly difficult to use, but it at least looks good.

Most of all, prospective buyers have realized that 200 meters of water resistance is more than adequate for almost any activity. And for, in some instances, less than one-third of the price of the MM300, the Baby Marinemaster just makes more sense. A buyer gets a similar case shape, great specs, a better bracelet, and a more basic movement for significantly less. In essence, the Baby has rendered the Marinemaster 300 to saturation niche status and perhaps the standing it always should have had.

Final Thoughts

No matter your choice, Seiko makes a great and dependable dive watch. If we look specifically at the Marinemaster 300 and the Baby Marinemaster, we’re talking about a near-flagship model and middle-range offering. Looking back over its history, there were probably very few who truly needed the Marinemaster 300, but it was so inexpensive. Also, while Seiko offered other models, none was perhaps as compelling as the Baby Marinemaster from a design and specs perspective. Furthermore, the Marinemaster has now become an expensive proposition and that makes the Baby all the more compelling. But these are just my thoughts. If it’s your money and your decision, to go all the way with the big dog or do you opt for two-thirds of the performance at one-third of the price?