Seiko Tuna S23631 & S23629 Dive Watches

The Seiko* Tuna… it’s a watch that has an immensely devoted set of followers and yet, it’s often forgotten, as it sits in the shadows of watches like the Rolex Deep Sea and other Seiko models from the SRP and SKX lineups. Like other Seiko watches announced for 2020, the Prospex Tuna is getting a subtle refresh. At first glance, I’m really excited to see a more classic silhouette behind the handset and pricing that isn’t entirely absurd; when you consider some of the previous Spring Drive and high-end automatic variants. With that, let’s take a quick first TBWS look at the new Seiko Tuna S23631 and S23629 Dive Watches.

Just to be clear, the S23631 is rated to 1000m and the S23629 is rated to 300m. Both of the watches feature the high-torque 7C46 quartz movement but the highly-rated S23631 features a blend of titanium and ceramic construction, while the S23629 comes in all-stainless steel. Both offer what you’d consider the ideal Tuna experience – it all just comes down to visual and material preferences, if you ask me. But, it’s also worth noting that the pricier S23631 also follows the more traditional top-loading, one-piece case design, which is a huge part of its delivered water resistance, while S23629 features a more straightforward screw-down caseback.


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If you head back and listen to our Hong Kong Watch & Clock Fair 2018 Megasode, you’ll probably hear me blabbering on about the SBBN033, which seems to be the official predecessor to the S23629 shown here. It’s a similar package but again, the absence of those ridiculous Monster hands really makes both of these watches way more enticing. Aside from the features listed above, I bet that both models come with insanely legible dials and a crazy application of lume. It’s almost as if these have been presented as the ultimate dive watch from Seiko. Not for desk divers… but for folks that actually want a tool that works deep below the calm blue sea.

Seiko S23631 & S23629 Specs

  • Case Diameter: 49.4mm(S23631) and 47.7mm(S23629)
  • Case Material: Titanium and ceramic(S23631) and stainless steel(S23629)
  • Water Resistance: 1000m (S23631) and 300m (S23629)
  • Movement: Seiko 7C46
  • Crystal: Sapphire
  • Strap: Rubber
  • Price: $2,400 (S23631) and $1,450 (S23629)


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The Seiko Tuna S23631 & S23629 dive watches will be available in July 2020. Learn more on Seiko’s official site. Seiko

Michael Penate( Co-Founder )

Michael Peñate is a first-generation American writer, photographer, and podcaster based in Seattle, Washington. His work typically focuses on the passage of time and the tools we use to connect with that very journey. From aviation to music and travel, his interests span a multitude of disciplines that often intersect with the world of watches – and the obsessive culture behind collecting them.


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