It’s been a relatively quiet start to the year for Seiko when it comes to the Prospex series. In the brand’s 145th year, we have seen some notable releases in the King Seiko, Seiko 5 Sports, and Presage series. However, new Prospex watches have been limited to a new Speedtimer released just after the new year began. But today, the brand unveils two new Prospex Marinemaster models that will most certainly appeal to fans of Seiko dive watches. Both the Prospex Marinemaster HBF001 and HBF002 are updated versions of the modern reinterpretation of the 1968 Diver. They introduce new dials, a new caliber, and an updated bracelet with a new clasp. As you will understand, there is plenty to discuss.
It’s not even been 18 months since Seiko updated its Marinemaster series with the SLA077 and SLA079, watches based on the classic reference 6159-7001, also known as the 1968 Diver. It was also the first time that it became clear that Seiko would use the Marinemaster name for multiple designs. As you may know, there are two Marinemaster series — one based on the 1965 Diver and another based on the 1968 Diver. For the latter, the brand is now upgrading its offerings with some very welcome updates. Besides a new caliber, a new bracelet with a toolless micro-adjustment system is a much-requested update that will greatly please enthusiasts. Let find out more about the two watches.
The story of the new Seiko Prospex Marinemaster HBF001 and HBF002
As is often the case with Seiko, this new duo of Prospex introductions consists of a limited-edition release and a regular-production model. We will get into the specifics of each in a bit, but first, let’s go over their similarities. The two models have a 42.6mm stainless steel case with a 14.1mm profile and a 49mm lug-to-lug.
These two watches are water resistant to 300 meters and feature a screw-down crown slightly above the 4 o’clock marker. The steel bezel features a black ceramic insert for the regular-production HBF001 and a blue ceramic insert for the limited-edition HBF002. The use of ceramic is an update from the steel bezel inserts of the previous models.
Both watches come with an updated five-row bracelet. It’s the same design as the previous generation. Although the design resembles the three-row bracelets found on many dive watches, the narrow, polished pieces are indeed separate links.
But the big update is the new folding clasp, which features a toolless micro-adjustment system. This offers a 16mm extension adjustable in 2mm increments. A nice detail is that you can retract the extension even while wearing the watch by simply pushing it in. Both the case and the bracelet also boast super-hard coating for improved scratch resistance and worry-free daily wear.
The update to the Seiko 8L45 movement
Another major update for both watches is the Seiko in-house caliber 8L45. We saw this movement used for last year’s Marinemaster SLA081 60th Anniversary edition and a series of King Seiko Vanac models. It is Seiko’s top-of-the-line offering that operates at 28,800 vibrations per hour, features 35 jewels, and offers a 72-hour power reserve. Caliber 8L45 replaces the 8L35 that powered the previous modern reinterpretations of the 1968 Diver.
Whereas the 8L35 was based on Grand Seiko’s 9L55 caliber, the 8L45 is based on the 9L65. To compare the two, the 8L45 movement increases the jewel count from 25 to 36 and improves the accuracy rating from -10/+15 seconds per day to -5/+10 seconds per day. Lastly, the power reserve is increased from 50 hours to a comfortable 72 hours. The caliber sits behind an all-steel case back, but it’s great to know that Seiko has chosen its best modern movement to power these watches.
The limited-edition Seiko Prospex Marinemaster HBF002
Now that we’ve addressed the similarities, it’s time to go over the differences between the two new models. Let’s start with the HBF002. This 1,000-piece limited edition was created in collaboration with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Seiko and JAMSTEC have had a longstanding collaborative relationship since the early 1980s. For decades, JAMSTEC has dedicated itself to marine research to advance science and technology and promote academic progress through various initiatives. During JAMSTEC expeditions, team members wear Seiko dive watches in extreme conditions to test their performance.
One of JAMSTEC’s efforts is the Arctic Research Program. As part of this special initiative, Japan’s first research vessel with icebreaking capabilities, the Mirai II — mirai (未来) meaning “future” in Japanese — will be completed this year, enabling data collection in ice-covered seas. The Mirai II inspired the design of the HBF002.
The textured dial features a special pattern depicting the trail forged by an icebreaker as it advances through sea ice. As you can see, the vertical gradient pattern is darker blue in the middle and lighter blue on the left and right edges of the dial. The textured dial also has a clear polished lacquer coating for extra visual impact. Hovering over the dial are the signature Lumibrite-filled Marinemaster hands. A nice touch is the gold-colored seconds hand, which adds some extra visual zing.
A vibrant dial that represents JAMSTEC’s Arctic research
Encircling the dial is a white ring with a dark blue minute track that complements the vibrant dial and the blue ceramic bezel insert with its white markings. To match the hands, the applied indexes on the dial all have a filling of light green Lumibrite. Located at 3 o’clock is a framed date window. It displays the date printed in black on a white date disc.
Another nice detail is the Lumibrite marker next to the date window on the minute track’s white ring. This small but thoughtful inclusion ensures a full set of luminous hour indexes. This special limited edition presents a vibrant aesthetic that symbolizes how JAMSTEC’s Arctic research paves the way for the future.
As mentioned, Seiko will produce 1,000 pieces of the limited-edition HBF002. They will be available starting in July 2026 at Seiko boutiques and select retail stores worldwide for €4,100.
The Seiko Prospex Marinemaster HBF001
The regular-production model that will interest most fans is the HBF001. At first glance, this new Marinemaster looks very much like its predecessor. Once you zoom in, though, you will find some visual differences. First, the new matte black dial features the date window at the 3 rather than the 4:30 position. I appreciate that update, as it creates a better visual balance. So does the wider, more modern font for the numerals on the bezel.
The dial features a refined texture similar to that of the previous model and has the same applied Lumibrite-filled indexes as the SLA079. The text on the lower half is slightly different, though, as it now says “Automatic 3 Days” instead of just “Automatic.” Overall, these are subtle differences, but I think the updates improve the watch quite nicely.
What has remained, though, is that typical Marinemaster feel that hasn’t changed ever since the brand introduced the Marinemaster SDBX001 in 2000. I especially like the case shape with its characteristic angular lugs and case sides. It’s one of the best case designs that Seiko ever created. The new Prospex Marinemaster HBF001 will be available starting in July 2026 at Seiko boutiques and select retail stores worldwide for €3,800.
Final thoughts on the new Seiko Prospex Marinemaster HBF001 and HBF002
We had a chance to try both of these new models, and they most definitely deliver! Both are substantial in size and presence, but they sit very well on my 18.5cm (7.3″) wrist. Granted, these are not watches for people with small wrists. But if you can pull off a 42mm watch, then it’s worth checking out these new Marinemaster models.
They represent the top of the line in the Prospex collection, and you can see and feel that. The visual updates make for a better-balanced overall design, the added functionality of the new clasp makes it more practical, and the new caliber adds great everyday performance and improved accuracy.
Understandably, along with these improvements come higher prices. Whereas the previous-generation SLA079 was €3,000, Seiko has increased the price of the updated HBF001 by €800. While that is significant, these updates bring the new Marinemaster to the top of the collection.
The other Marinemaster references based on the 1965 Diver currently cost €3,400. Considering the new upgrades to the 1968 Diver design, the price increase makes sense in Seiko’s current collection. On top of that, the new Marinemaster models are still hard to beat, even at their higher prices. It’s great to see this design getting frequent updates and carrying on the torch that made the first Marinemaster legendary among Seiko enthusiasts.
Jorg Weppelink
2026-03-18 06:00:00