Omega Seamaster is a name that commands respect from fans of luxury dive watches. Since 1957, the Seamaster has held the line against its eternal rival from Geneva, the Rolex Submariner, but the latest generation of Omega Seamaster Professional Planet Ocean Co-Axial Chronograph packs the tech and taste to gain a jump on the stolid "Sub." Omega opens its volley with equal measures of class and mass; the 45.5mm stainless steel case features a full-bodied presence that surpasses the comparatively dainty Submariner's 40mm span. Enthusiasts with large wrists or Hublot-era standards of case size will find the Omega Seamaster Planet Ocean Chronograph the perfect go-to when the mantra is "go-big or go home." More than a big fella, the Seamaster Planet Ocean 600M Co-Axial Chronograph is a sophisticated companion that offers its owner the advantages of Swatch Group's formidable materials science labs. A ceramic unidirectional diving bezel laughs at the kind of physical insults that used to generate Swiss landfill in the era of metal bezel inserts. Remember that "weathered bezel" look that left every vintage dive watch looking like a flea market refugee? Forget it, because ceramic matches the scratch resistance of a sapphire crystal, and only diamond can reliably scratch this kiln-fired metallic hybrid. Inside its burly ferrous carapace, the Omega Seamaster Planet Ocean 600M benefits from the refinement of Omega's exclusive in-house caliber 9300 co-axial movement. With an anti-magnetic silicon hairspring and escapement, a shock-resistant free sprung balance wheel and dual-anchored balance bridge, and a superb 60-hour power reserve, this COSC automatic chronometer races ahead of conservative Rolex in the tech department. A standard helium release valve keeps a lid on the works when accumulated nitrogen of exotic gas environments asserts itself during post deep-dive ascents. And check out the three-link stainless steel dive bracelet. While Omega's Seamaster line has featured some of the finest bracelets of recent decades, the Planet Ocean 600M Co-Axial Chronograph sets a new standard. Each link is beautifully finished and supple on the skin, but the piece is more than comfortable; it's formidable to behold and reassuringly solid. The Planet Ocean bracelet is rock solid, and it boasts a clasp to match. With twin-trigger actuation, the clasp offers the kind of security that no friction-fit competitor can match. Even better, the clasp offers one of the best deployant dive extensions in the business; it's equally useful over a dive suit or a winter coat. Video and content by Tim Mosso.