With only 600 pieces worldwide, this limited-edition design commemorates 60 years of Seiko’s heritage in innovative and reliable diving watches, which began with the 1965 launch of Japan and Seiko’s first ever Diver’s watch.

This latest timepiece takes its inspiration from a key milestone in Seiko’s diving watch expertise – the 1968 Diver. This was the brand’s first one-piece case hi-beat Diver’s watch, with 300m water resistance. The 2025 Marinemaster is Prospex’s most advanced model yet – crafted from lightweight titanium for comfortable wearability. The superhard coating on the case and bracelet is paired with a DLC (Diamond-like Coating) on the bezel, for added scratch resistance.

The Prospex ‘Shinkai’ will join the Japanese Agency for Marine-Earth Science and Technology (JAMSTEC) research team on their 2025 Arctic research expedition. Prospex and JAMSTEC have a long history together of enduring challenging environments, where the watches have been successfully put to the test in extreme conditions, far outperforming expectations. In 1983, two 600m Diver’s watches were depth tested onboard the ‘Shinkai 2000’ – a research submersible, in 2014, both a quartz and an automatic 1000m Saturation Diver was tested onboard the ‘Kaiko 7000’, surpassing its specifications by continuing to perform at 3000m depth.

Under a dual-curve sapphire glass is a blue dial made with a new structure of layered transparency, designed to express the ocean – as in its name ‘Shinkai,’ meaning deep sea in Japanese. The bracelet of this watch features a micro-adjustable clasp feature.

Crafted at the Shizukuishi Watch Studio, where Seiko’s finest mechanical calibres are developed, this robust Marinemaster is powered by the new in-house 8L45 movement – accurate to +10/-5 seconds per day, with a three day power reserve. This saturation Diver is water resistant for up to 600m.

Prospex is a combination of the words ‘Professional’ and ‘Specifications.’ Seiko Prospex timepieces are designed to be practical, reliable and durable; to meet the high standards required in extreme environments for sports lovers and adventure seekers alike.