Sea Quartz 30 [42mm] - Black

Sale price$295.00 USD
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Band: Stainless Steel

The Dive Watch That Started It All

Original spec. Modern upgrades. Legendary status.

Before launching Momentum, our founder Simon and his family introduced the Sea Quartz 30 in 1977 under the Chronosport name one of the first analog quartz dive watches on the market. It quickly became a favorite among military divers and even made its way onto the wrist of Tom Selleck in the first three seasons of Magnum P.I..

Rebuilt from the original case design and upgraded with modern materials, the new Sea Quartz 30 stays true to its roots: rugged, reliable, and ready for anything.

High-Torque Swiss Movement – Built for maximum durability and long-term accuracy.
✅ Sapphire Crystal – Scratch-resistant and vintage-inspired, just like the original.
300M Water Resistance – With screw-down crown and caseback for real dive performance.
Matte 316L Stainless Steel Case – Bead-blasted for a no-glare, no-nonsense finish.
Super-LumiNova® Hands & Markers – Glows bright through the night for effortless readability.
Assembled in Canada – Designed and tested for life in and out of the water.
Magnum P.I. Approved – A direct descendent of the iconic watch worn by Thomas Magnum himself.


  • Movement Swiss, Quartz (Battery), Ronda R507
  • Dial Color Black
  • Screw-down crown
  • Water Resistance 300 / 990
  • SKU: 054AADAFC-AB-B-AC-B-AC-CLKA-D-A-B
  • Battery: 371

The Original Magnum P.I. Watch

In the early 1980’s, CBS launched the TV series Magnum PI. Set in Hawaii, it starred Tom Selleck. The series consistently ranked in the top 20 U.S. television programs for several years, finishing as high as number 3 for the 1982–83 season. And the watch that Tom Selleck wore for the first 3 seasons? Of course, it was the original Chronosport Sea Quartz 30.

Authentic History, Better Performance

The Sea Quartz 30 models from the 1980’s have built an almost cult-like following with Magnum fans, divers, and watch fanatics. To make them proud, we recreated the Sea Quartz 30 as closely as possible to the original. Our historical connection to Chronosport meant we could send genuine cases, dials, hands, and bezels directly to our factories so they could analyze and match the design. Of course, we wanted to make some key improvements. The dial, hands, and bezel now feature C3 Super-LumiNova for vastly improved lume performance over the original. The original watch also featured a mineral bezel and crystal, which has been replaced with scratchproof sapphire for unmatched durability. What we didn’t change is the iconic design.

WE DO THINGS OUR WAY.

St. Moritz Watch Corp. designs, assembles and services high quality sports watches under the MOMENTUM® brand. As life becomes more active and a more casual style becomes the norm, our straightforward designs, with outstanding waterproof performance and no-BS pricing, resonate more and more with active people everywhere.