The Hazard 4 Heavy Water Diver in Blackout finish is a 50mm Grade 2 titanium dive watch powered by a Ronda 515 Swiss quartz movement and fitted with self-contained tritium gas-tube illumination on every marker and hand. At approximately 3.8 oz on the wrist, the titanium case is half the weight of a comparable steel case while offering double the tensile strength. Water resistance is rated to 300 m / 990 ft, and the sapphire crystal is anti-reflective coated on the interior. The Blackout variant pairs a PVD-black case finish with a custom bracelet band and ships in a military-grade thermoformed travel case.

Who this is for

• Dive and water sports enthusiasts: a 300 m depth rating, screw-down crown, and uni-directional 60-click bezel make this a fully functional dive tool.
• Professionals who need reliable low-light readability: tritium gas tubes glow continuously without charging — no UV exposure needed, no fade by morning.
• EDC-focused wearers who work across formal and field environments: the 3D stencil numerals, sapphire crystal, and PVD-black finish read as dress-capable without sacrificing toughness.

Tritium illumination

Unlike luminescent paint that requires UV charging and fades within hours, the Heavy Water Diver uses self-contained tritium (H3) Swiss mini-lamps — the same technology found in quality pistol night sights. Tritium glows through natural radioactive decay, requiring no charging and no external light source. The vials sit 80% above the dial surface rather than flush-inset, which makes them visible from oblique angles and around the edges of the case, not only when viewed straight-on. Tritium has a half-life of 12 years: after 12 years the tubes will be half as bright as they are today, still functional but progressively dimmer over time.

Case and crystal

The 50 mm case is machined from Grade 2 titanium with a bead-blast finish on the natural variant and PVD black on the Blackout. Titanium at this grade is hypoallergenic, corrosion-resistant, and substantially lighter than 316L stainless without sacrificing structural integrity. Case thickness is 15 mm. The crystal is scratch-resistant sapphire with an anti-reflective coating applied to the interior surface to reduce glare without adding an exterior coating that could wear away. The case-back and crown both screw down to maintain the 300 m water resistance rating. The crown is sized and knurled for easy operation with wet or gloved hands.

Dial and bezel

The dial layout combines 3D military stencil-cut numerals in a two-layer design with an angled minutes inner-dial and an integrated 24-hour military time scale — both uncommon on a single dial. The hour markers are machined into the bezel rather than printed, so they will not scratch off with use. The uni-directional bezel delivers 60 audible clicks per rotation and carries a tritium zero-marker at the 12-position porthole. Uni-directional rotation ensures that any accidental bump of the bezel can only cause elapsed time to read longer, never shorter — a critical safety feature for dive timing.

Movement and power

The Ronda 515 is a Swiss-made quartz movement with a date complication positioned at 4 o'clock. Battery type is 371 silver oxide, mercury-free. Standard battery life runs approximately 2 years from the day of installation; exposure to sustained heat or cold will affect that interval. The movement is battery-powered and does not require winding or rotor servicing.

Strap and included hardware

The Blackout ships mounted on a custom bracelet band. Strap horn width is 24 mm. The watch uses user-serviceable fast-change screw-in strap pins, removable with a Torx 6 screwdriver or bit (not included), which means strap swaps require no spring-bar tool and no watchmaker visit. Each watch includes one military-grade thermoformed travel case.

Specifications

Frequently asked questions

What makes tritium illumination better than standard lume?

Yes — tritium gas tubes glow continuously through natural decay, with no charging required and no fading overnight. Standard luminescent paint (lume) must absorb light to glow and loses brightness within a few hours in darkness. The trade-off is longevity: tritium output diminishes gradually over its 12-year half-life, while fresh lume at peak charge can be brighter in the first minutes after exposure.

Is a 50mm case too large for everyday wear?

It depends on wrist size and preference. At 50 mm the Heavy Water Diver is a large watch by any standard, though reviewers note it wears smaller in person than it appears in photos. The Grade 2 titanium case keeps total wrist weight to approximately 3.8 oz, which reduces the perception of bulk compared to a steel watch of similar diameter.

How does the screw-down crown affect daily use?

The screw-down crown must be unscrewed before setting the time or date and screwed back down afterward to maintain the 300 m water resistance rating. The crown on the Heavy Water Diver is large and knurled for grip, which makes the unlock-and-relock process straightforward. The full booklet and how-to video linked on the product page walk through the procedure step by step.

Can I change the strap myself?

Yes. The Heavy Water Diver uses screw-in strap pins rather than spring bars. A Torx 6 screwdriver or bit — not included — is all that is required. This makes strap swaps a tool-simple job without a watchmaker. The 24 mm horn width is a standard aftermarket size with broad third-party strap availability.

How long will the battery last and what type does it use?

The Ronda 515 runs on a 371 silver oxide battery, which is mercury-free and widely available. Expected life is approximately 2 years from the date of installation. Heat and cold exposure can shorten that interval. Battery replacement is a standard watchmaker service at any jeweler or watch shop and does not require returning the watch to the manufacturer.

Is this watch suitable for formal or office wear?

Yes. The 3D stencil numerals, sapphire crystal, and PVD-black finish give the Blackout a dial presence that reads as a dress watch despite the tactical brief. Several reviewers describe it as business-appropriate. The thermoformed travel case makes it a practical gift or travel companion for professionals who move between field and formal environments.