Seiko’s new Prospex Marinemaster 1968 Heritage Save the Ocean Limited Edition, reference HBF003J, is a diver with a deep green dial inspired by the mangrove forests of Okinawa and rose-gold-coloured details. Seiko’s UK online store lists it at £3,300 with a scheduled release of November 1, 2026, and gives a worldwide edition of 900 pieces. The specifications below are the manufacturer’s listed figures, not measurements taken for this article.
Reference and edition size
The model is the Prospex Marinemaster 1968 Heritage Save the Ocean Limited Edition, reference HBF003J. The Seiko Official UK Online Store lists the edition at 900 pieces worldwide, and that figure is the one to quote for global supply.
Seiko’s Japanese online store also returns HBF003J under the Marinemaster 1968 Heritage Save the Ocean name, which confirms the reference. The specifications in this article come from the UK listing. A European Seiko boutique listing uses the code HBF003J1 for the same model name. The available listings do not explain the trailing digit, so check the reference printed on the box or warranty card with the retailer before ordering.
The mangrove-inspired dial
According to the UK listing, the dial draws on Okinawa’s mangrove forests. It is deep green, with rose-gold-coloured accents on the hands and surrounding details. The listing presents the colour story as retailer copy rather than a quotation from a named Seiko designer, so the mangrove inspiration should be attributed to the listing.
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#1 Best Overall
- STAINLESS STEEL BRACELET for a durable and timeless accessory paired with a multi-row design that enhances the style of this analog watch
- BOX-SHAPED CRYSTAL adding a sophisticated touch and enhancing the smooth curves of the profile, creating a pleasing shape on the wrist
- MULTI-FUNCTION CHRONOGRAPH with precise timekeeping and a nod to automotive elegance
- WATER RESISTANT DESIGN ensures your wrist watch is ready for any adventure, rain or shine
- HIGH-CONTRAST SUBDIALS for superior visibility and a vintage appeal in this stylish analog watch
The listing also describes the watch as a re-interpretation of Seiko’s 1968 diver, with a case design drawn from that reference and the Marinemaster name carried over. The same copy calls the 1968 original the world’s first hi-beat diver. That is Seiko’s own claim, repeated by the retailer, and it is not an independently verified historical fact.
Case, bracelet and listed dimensions
The listing gives the following physical details:
- Materials: stainless-steel case and bracelet.
- Case diameter: 42.6 mm.
- Thickness: 14.1 mm.
- Case length: 49.3 mm, as listed.
- Lug width: 20 mm, which determines the strap or bracelet width the case accepts.
- Crystal: dual-curved sapphire with an inner anti-reflective coating.
- Crown position: 4 o’clock.
- Bezel: unidirectional.
- Lume: Lumibrite on the hands, indexes and bezel.
- Clasp: three-fold clasp with a secure lock, push-button release and slide adjuster.
The listing does not include hands-on wear impressions or comfort assessments, so the sources here cannot say how the 42.6 mm case sits on a particular wrist.
Rank #2
- STUNNING BLUE DIAL: this automatic men's watch features a deep blue, pressed pattern and gloss finish surrounded by a stainless steel watch case
- AUTOMATIC: these self-winding, automatic men's watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: features a durable stainless steel watch case and bracelet with see through caseback
- WATER-RESISTANT: these men's wrist watches are water-resistant down to 50 meters
- 4R35 CALIBER: equipped with the reliable caliber 4R35 automatic movement, this accurate men's watch keeps precise time
Movement and listed performance
The watch runs on the automatic Seiko calibre 8L45. The listed specifications are:
- Jewels: 35.
- Beat rate: 28,000 vibrations per hour (8 beats per second).
- Display: date.
- Power reserve: 72 hours.
- Stated accuracy: +10 to -5 seconds per day.
- Magnetic resistance: 4,800 A/m.
These are Seiko’s stated figures. No independent timing or power-reserve test is available for this model, and the accuracy range should be read as the manufacturer’s tolerance.
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- STAINLESS STEEL CASE built to endure with style, making this watch your perfect daily companion
- AUTOMATIC MOVEMENT for seamless precision in every tick of this watch
- SCRATCH-RESISTANT CRYSTAL to maintain a pristine look even with daily wear and tear on your watch
- LUMINESCENT HANDS for effortless readability in low-light conditions, ensuring you never miss a moment with this watch
- WATER RESISTANT DESIGN ensuring your watch is ready for any adventure, rain or shine
Water resistance
The listing states 300 m water resistance. Read this as the manufacturer’s rating for the case as sold. It is the figure to compare against other divers, and it does not replace the care guidance in the box or warranty documents.
Price, release timing and where it is listed
- Price: £3,300, as shown on the Seiko Official UK Online Store. This is a UK retailer price. The listing does not establish prices in other currencies or markets.
- Release date: November 1, 2026, as listed. That date is in the future relative to this article.
- Availability: the UK listing showed preorder status when it was checked. Stock and status can change, so confirm them with the retailer before buying.
- Edition size: 900 pieces worldwide, per the same listing.
Treat the price and timing as UK listing facts. Other regions may see different prices, stock arrangements or dates.
Rank #4
- STUNNING BLUE DIAL: this rugged sports watch features a beautiful Manta Ray-patterned blue dial, with Lumibrite dial indicator hands and markers for low light and a magnified day/date calendar
- BLACK BEZEL: this versatile men’s watch features a black ceramic unidirectional bezel with distinctive scalloped edging, for elapsed timing
- AUTOMATIC & MANUAL: SRPF77 automatic watches for men power up with your natural movements, and feature the ability to wind manually, with 41 hours of reserve power
- WATER-RESISTANT: these rugged stainless steel dive watches for men feature a deep blue silicone strap and are both stylish and robust, following ISO standards for scuba, and are water-resistant to 200 meters
- 4R36 CALIBER: equipped with the reliable 4R36 caliber, these precise men’s wrist watches ensure the most accurate timekeeping
What is and is not established
- Established: the reference, the mangrove-inspired design story, the listed case, movement and water-resistance specifications, the UK price, the November 1, 2026 release date and the 900-piece worldwide edition size, all as stated by Seiko’s UK store.
- Not established: independent testing of accuracy, power reserve or water resistance; on-wrist comfort; stock outside the UK listing; and the meaning of the HBF003J1 code seen on a European boutique listing.
- Attribution: the 1968 “world’s first hi-beat diver” claim and the mangrove colour story come from retailer and brand copy, not from a named spokesperson.
Before buying, confirm the reference, the price in your currency and the release or stock status directly with an authorised Seiko retailer.
Quick Recap
Best Value
- AUTOMATIC MOVEMENT: Seiko 4R35 automatic movement includes manual winding, 23 jewels, date display, stop-second function, and approximately 41 hours of power reserve.
- 200M DIVER'S WATER RESISTANCE: Rated to 200 meters / 660 feet for diving, with a screw-down crown and screw case back.
- STAINLESS-STEEL CASE: 41.7mm stainless-steel case measures 12.3mm thick with a 49.5mm lug-to-lug distance and 20mm lug width.
- HARDLEX CRYSTAL: Durable Hardlex crystal protects the dial, while LumiBrite on the hands, indexes, and bezel improves low-light visibility.
- DIVER-READY DESIGN: Unidirectional rotating bezel and three-fold clasp with secure lock, push-button release, and extender provide practical functionality.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
