The Prospex Marinemaster upholds Seiko’s longstanding
legacy of bold exploration in a collaboration with JAMSTEC.

Seiko’s journey in diver’s watchmaking began in 1965 with Japan’s first diver’s watch, which accompanied members of the Japanese Antarctic Research Expedition to the South Pole from 1966 to 1969. This model was followed by the creation of the nation’s first 300m water-resistant diver’s watch in 1968. In the decades since, Seiko has developed new technologies, designs, and features that have made its diver’s watches a trusted favorite among professionals and enthusiasts worldwide.

The company’s legacy of testing the limits of the modern sports watch and supporting marine conservation continues through its partnership with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which began in the 1980s. In 1983, two professional diver’s watches rated to 600 meters were successfully tested aboard SHINKAI 2000, a manned research submersible operated by JAMSTEC.

For decades, JAMSTEC has been engaged in marine research to advance science and technology and promote academic progress through various initiatives. One such effort is the Arctic Research Program. As part of this, Japan’s first research vessel with icebreaking capabilities, Mirai II (the word mirai means “future” in Japanese), will be completed this year, enabling data collection in ice-covered seas.

Inspired by the spirit of bold exploration that connects JAMSTEC and Seiko, two new diver’s watches join Prospex’s flagship Marinemaster series. The first is a JAMSTEC collaboration, and the second is a continuous production model. Both are powered by Seiko’s self-winding Caliber 8L45 mechanical movement and represent the pinnacle of the Seiko 300m water-resistant diver’s watch.

Honoring a spirit of exploration and forging new paths

The collaboration model showcases a new textured dial that imagines the trail forged by an icebreaker as it advances through sea ice, symbolizing how Arctic research paves the way for the future. Its vertically oriented blue gradient, which deepens at the center, is finished with a thick, clear coating and then polished, echoing the boundless, crystalline depth of the Arctic Ocean. The blue ceramic bezel enhances the beauty of the dial while providing exceptional scratch resistance.

The ultimate expression of a classic Seiko diver’s watch

As the first continuous production Prospex watch powered by the 8L45 movement, the new black-dialed creation embodies the classic 1968 diver’s design, ensuring exceptional legibility underwater. The dial’s deep black hue and fine-grain texture minimize light reflection from the dial while the beveled edges of the indexes catch light from any angle, delivering high visibility.

An evolution of the Marinemaster

Both creations feature an updated clasp that offers easy adjustments of up to 16mm in 2mm increments by sliding the button inside. Even when the clasp is closed, the extension can be retracted, ensuring comfortable and effortless operation.

While its exterior traces the familiar contours of the 1968 diver’s watch—including its flowing silhouette and a screw-down crown at 4 o'clock—the Caliber 8L45 that powers the watches represents the summit of Seiko’s mechanical watch movements. The mainspring and hairspring are made of Spron, Seiko’s proprietary alloy. The movement offers 72 hours of power reserve thanks to a mainspring that is long and thin, and operates within a tolerance of +10 to -5 seconds per day. To ensure the watch's durability, the crown is not screwed directly into the case but locked into a separate component that is built into the case, allowing it to be more easily replaced.

The two creations will be available at select Seiko Luxe retailers nationwide from July 2026, with the JAMSTEC collaboration model offered as a limited edition of 1,000.

About JAMSTEC

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is a national institute for comprehensive marine research and development dedicated to advancing innovative science and technology. JAMSTEC fosters academic progress, and deepens understanding of the Earth and life, while contributing to the sustainable development of society and the preservation of the global environment. Using data obtained through its research, JAMSTEC strives to address societal and economic needs and drive innovation across multiple sectors.

Seiko Prospex Marinemaster 1968 Heritage Diver’s Watch

Seiko Prospex Marinemaster 1968 Heritage Diver’s Watch JAMSTEC Limited Edition

Caliber 8L45
Driving system: Automatic
Frequency: 28,800 vibrations per hour (8 beats per second)
Power reserve: 72 hours
Number of jewels: 35

Specifications
Stainless steel case and bracelet with super-hard coating
Three-fold clasp with push button release, solid & slide adjuster
Dual-curved sapphire crystal with anti-reflective coating on the inner surface Bezel with ceramic insert
Screw-down crown, screw case back
Lumibrite on hands and indexes
Water resistance: 300m diver’s
Magnetic resistance: 4,800 A/m
Diameter: 42.6mm, Thickness: 14.1mm
Recommended retail prices in USA: $3,600 (HBF001), $3,900 (HBF002)
Limited Edition of 1,000 (HBF002)

For further information:

Special web page:
https://www.seikowatches.com/us-en/products/prospex/special/1968_mm_2026/

Seiko Prospex web page:
https://www.seikowatches.com/us-en/products/prospex

Note:
The specifications and price information in this release are as of the published date and are subject to change.