Introducing: The Seiko Prospex Marinemaster Divers HBF001 And HBF002 JAMSTEC Limited Edition

What We Know

Seiko continues to build on its long-standing association with professional diving and marine research with two new additions to the brand’s higher-end Marinemaster line. Including a brightly textured reference released in partnership with JAMSTEC (Japan Agency for Marine-Earth Science and Technology), these new models follow the 300m Marinemaster template while introducing updated materials, a new movement, and some additional tweaks over the previous model. Also representing a price jump over the preceding model, these new divers sit at the top of the range for Seikos, with 300 meters of water resistance and 8L-series movements. 

Both of these new Marinemaster references share the same specs and differ only by colorway and the fact that the JAMSTEC model (no relation) is limited to 1000 pieces. Both use stainless steel cases measuring 42.6mm across and 14.1mm thick, with 300 meters of water resistance and a screw-down crown at 4 o’clock. A dual-curved sapphire crystal sits above the dial, and the unidirectional dive bezel features a ceramic insert color-matched to the dial. 

While the black-dialed HBF001 model hits the classic Marinemaster look, the JAMSTEC limited-edition HBF002 features a vertically graded blue dial with a textured surface inspired by polar icebreaking, offering a unique look and feel. Both references come fitted to a steel bracelet and a newly updated clasp offering on-the-fly micro-adjustment of up to 16mm in 2mm increments. The adjustment is controlled via a button on the inside of the folding clasp (shown in an image below). 

Inside, both models are powered by Seiko’s automatic Caliber 8L45. This is the first time that a production Prospex diver has used this movement, and the 8L45 is positioned at the higher end of the brand’s mechanical lineup (before Grand Seiko enters the conversation). It runs at 4 Hz and offers a 72-hour power reserve, with stated accuracy of -5 /+10 seconds per day. The movement uses Seiko’s proprietary Spron alloys for the mainspring and hairspring, contributing to durability and stability over extended use. Seiko has also revised the crown construction so that it interfaces with a separate component rather than threading directly into the case, a change aimed at improving long-term serviceability.

Pricing is set at $3,600 for the standard black-dial HBF001 and $3,900 for the JAMSTEC limited-edition HBF002, which is limited to 1,000 pieces. Both models are expected to be available starting July 2026 through Seiko Luxe retailers.

What We Think

On paper, and in Seiko’s current lineup, both of these new references fit the role for high-spec Seiko divers, and both look like really solid options for someone wanting a top-tier Seiko diver (even if they’ve seemingly scuttled the “SLA” moniker). That said, it’s worth considering the realities of previous (and similar) Prospex models to understand both the price changes and the spec changes. Given that the HBF002 is both an LE and a special color way (one that I rather like), let’s try to compare apples to apples with the new HBF001 and the previous SLA079.

The SLA079 is a 42.6mm steel/black dial 300m Marinemaster that is 13.4mm thick, has a steel bracelet (without push-button microadjustment), and uses Seiko’s 8L35 movement (50 hours of power reserve, 4 Hz, rated for -10/+15 seconds a day). To keep it simple, that means the new HBF001/002 is a bit thicker, has a longer power reserve (70 vs. 50 hours), is more accurate (-5 to +10/day), and comes with the microadjust-equipped bracelet. 

Those are all solid improvements, but they come with a price. The SLA079 has a retail price of $2,900, while the new HBF001 is $700 more. Also, while not specifically a measurable improvement (more of a subjective one), the HBF001 has its date window at 3 o’clock, while the SLA079’s is at 4:30. Interestingly, the HBF001 appears to use a white date wheel vs the dial-matched black wheel of the SLA079, and only the LE HBF002 has a frame around the date aperture. 

In the current SJE/SLA range, the starting price sits around $2,800 for 200m options like the SJE101 (I know this because I have the tab saved, it’s like an SPB143 but a bit smaller and taken to the next level–I need one). Well on the way to $4,000, it’s clear that Seiko sees these models as competition for Tudor’s Black Bay and Pelagos, so it’s fitting that we see refinements like the micro-adjustment in the clasp and more specific timekeeping. 

In a market where just about all watches seem to be getting more expensive, this bump in price is at least balanced with the inclusion of the higher spec movement and the more ergonomic bracelet, all of which are notable and push closer to what someone might be looking for from Grand Seiko, Tudor, or Longines. Like with the aforementioned SJE101, the new HBF001 now sits atop the list of Seikos that I’d love to check out in person sometime soon. Perhaps a summer dive trip is in order. 

The Basics

Brand: Seiko  
Model: Prospex Marinemaster 1968 Heritage & JAMSTEC Limited Edition
Reference Number: HBF001 and HBF002

Diameter: 42.6mm
Thickness: 14.1mm
Case Material: Steel with Seiko’s Super-Hard coating
Dial Color: Black or ice-themed blue (for HBF002 LE)
Indexes: Applied
Lume: Yes, hands and markers
Water Resistance: 300 meters
Strap/Bracelet: Steel bracelet with push-button microadjustment in clasp.

The Movement

Caliber: Seiko 8L45
Functions: Hours, minutes, seconds, date
Power Reserve: 72 hours
Winding: Automatic
Frequency: 28,800 vph
Jewels: 35
Chronometer Certified: No

Pricing & Availability

Price: $3,600 for HBF001 (black dial), $3,900 for HBF002 LE
Availability: From July 2026 via Seiko Luxe retailers worldwide
Limited Edition: The HBF002 is limited to 1000 pieces. 

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