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Seiko continues to invest in one of its strongest categories, professional diver’s watches, introducing two new additions to the Prospex Marinemaster series for 2026. These two creations—one developed in collaboration with the marine research organization JAMSTEC and one joining the core collection—express the same philosophy in different ways: the evolution of a tool shaped by real-world conditions.
Seiko, which celebrates its 145th anniversary this year, began the year with four commemorative limited editions across the King Seiko, Astron, Presage, and Prospex collections. The brand’s relationship with diving runs deep, dating back to 1965, when Japan’s first diver’s watch accompanied the national Antarctic Research Expedition. In the years that followed, the company developed technologies and solutions that helped define the diver’s watch category, from early 300-meter water-resistant models to professional 600-meter watches tested in real missions aboard the SHINKAI 2000 submersible in the 1980s. Within this context, Seiko’s partnership with JAMSTEC represents the natural continuation of a shared path grounded in research and ocean exploration.
The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is a national institute dedicated to comprehensive marine research and development, with a focus on advancing scientific and technological innovation. JAMSTEC promotes academic progress and deepens our understanding of the Earth and life, while contributing to the sustainable development of society and the preservation of the global environment. By leveraging the data generated through its research, the organization aims to address social and economic challenges and drive innovation across multiple sectors. With this in mind, let us begin with the watch Seiko created in collaboration with this institution.
The first of the two new Marinemaster models is a limited edition of 1,000 pieces, drawing its inspiration from Arctic expeditions and, more specifically, from the path of an icebreaker moving through frozen seas. The dial captures this idea through a striking vertical gradient of blue tones that deepen toward the center, creating a strong sense of depth. Its surface features a distinctive texture reminiscent of the trail left behind as the vessel cuts through the ice, while a thick, glossy coating enhances clarity and luminosity, evoking the almost crystalline quality of Arctic waters.
A blue ceramic bezel completes the composition while offering increased scratch resistance. On the caseback, the inscription “JAMSTEC LIMITED EDITION” alongside the individual numbering emphasizes the collectible nature of this release.
Price: €4,100
Watch the timepiece in action in the video below…
Alongside this more expressive version, Seiko introduces a second model that focuses on clarity and functionality. Featuring a black dial and a matching ceramic bezel, this new Marinemaster is the most direct reference to the historic 1968 diver, adopting the familiar layout that ensures excellent legibility underwater.
The dial’s fine-grained texture helps reduce reflections, while the beveled surfaces of the hands and indexes are designed to catch light from different angles, enhancing visibility in demanding conditions. This model also carries particular significance, as it is the first regular-production Prospex watch powered by the new Caliber 8L45.
Price: €3,800
Watch the timepiece in action in the video below…
Powering both models is the automatic Caliber 8L45, a movement that represents the highest level of Seiko’s mechanical expertise in the field of diver’s watches. Thanks to a long and thin mainspring, it delivers a power reserve of 72 hours and operates within a daily accuracy range of +10 to -5 seconds. The use of Seiko’s proprietary Spron alloy for both the mainspring and the hairspring contributes to the movement’s stability and durability. Of particular interest is also the construction of the crown, which is not screwed directly into the case but secured within a separate integrated component, making maintenance easier while enhancing overall robustness.
Both Prospex Marinemaster 1968 models are crafted in stainless steel with a super-hard coating, measuring 42.6 mm in diameter and 14.1 mm in thickness, and offering water resistance up to 300 meters.
Their case retains the characteristic silhouette of Seiko’s 1968 diver, with flowing lines and a screw-down crown positioned at 4 o’clock, a detail that is both ergonomic and instantly recognizable.
The bracelet is fitted with a clasp featuring an updated secure adjustment system, allowing micro-adjustments of up to 16 mm in 2 mm increments via a push-button mechanism. This functionality ensures enhanced comfort in everyday wear, even as conditions such as temperature or activity levels change.
The two new Seiko Prospex Marinemaster models will be available from July 2026 at selected Seiko boutiques and retail partners worldwide. The JAMSTEC collaboration will be released in 1,000 limited pieces, while the black-dial version becomes part of the brand’s permanent collection.
