Ref. 03 · Topic
Dive watches
A dive watch is built around a one-way timing bezel, strong lume and real water resistance. The depth printed on the dial is a test pressure, not a safe diving depth.
- ISO 6425 minimum
- 100 m, tested to 125% of the rating
- Bezel
- turns one way only, so a knock can only shorten the timed dive
Water resistance ratings come from a static pressure test in a lab (1 bar is about 10 m). Real swimming adds movement, temperature changes and aging seals, which is why a 30 m watch is not meant for swimming. The water resistance decoder shows what each rating is commonly considered good for.
A watch marked DIVER'S with a depth is made to ISO 6425. The standard asks for at least 100 m, an overpressure test to 125% of the rating, a unidirectional bezel or other preselected time indicator with minute marks, readability at 25 cm in the dark, a running indicator visible in the dark, and tests for magnetism, shocks and salt water.
To time a dive, or a parking meter, turn the bezel so its triangle lines up with the minute hand. Elapsed minutes are then read on the bezel where the minute hand points. Check that the crown screws down and that the lume on the hands and the bezel pip is bright enough for your use.
Tool for this topic
Common mistakes
- Treating the printed depth as how deep you can go.
- Swimming with a screw down crown left unscrewed.
- Skipping a water resistance test after a service, a crystal change or a few years of wear.
Pages on this topic
- Why some dive watches have helium valvesWhat a helium escape valve does, why saturation divers needed one, the difference between automatic and manual valves, and why most owners never use it.Explainer
- What makes a real dive watch: ISO 6425 explainedISO 6425 sets the tests a watch must pass to say DIVER'S on the dial: at least 100 m, an overpressure test, a timing bezel, night legibility and more.Explainer
- Watch water resistance ratings explained: 30, 50, 100 and 200 mWhat 30 m, 50 m, 100 m, 200 m and 300 m water resistance ratings mean in real life, why 30 m is not 30 meters deep, and when a watch is truly a diver.Explainer
- Watch lume explained: LumiBrite, Super-LumiNova and how to charge itHow watch lume works, LumiBrite vs Super-LumiNova vs tritium, why some dials glow all night and others fade fast, and how to charge lume properly.Explainer
- Is the Tissot PRX waterproofThe Tissot PRX is water resistant to 10 bar (100 m). What that means for swimming, showers and the beach, why it is not a dive watch, and when to check the crown.Explainer
- How to use a dive watch bezelHow to use the rotating bezel on a dive watch: line up the triangle, read elapsed time, and why the bezel only turns one way. Works for dives, parking and cooking.How-to
- Dive watch straps: rubber, NATO, bracelet or leatherWhich dive watch strap suits water, heat and a dressier day: rubber, silicone, NATO, steel bracelet or leather, plus how to get the lug width and fit right.Explainer
Gear for this topic
- Best Seiko dive watches: Turtle, Monster, Samurai and 5 SportsEight Seiko dive watches compared by case size, lug to lug, movement, crystal and water rating, from the 5 Sports SRPD59 to the King Samurai.Gear guide
- Best automatic dive watches under $500Seven automatic divers under $500 from Seiko, Citizen, Orient, Bulova and Caravelle compared by ISO claim, water resistance, crystal and bezel.Gear guide
- Best dive watches under $1,000Eight dive watches under $1,000 compared on stated case size, movement, power reserve, water resistance and crystal from each Amazon listing.Gear guide
- Best dive watches for women and smaller wristsSix dive watches for women and smaller wrists from Certina, Tissot, Hamilton, Mido and Bulova compared by case size, thickness, movement and water resistance.Gear guide