A watch marked 5 bar or 50 metres is not automatically safe to wear 50 metres underwater. The rating describes resistance to pressure under specified test conditions; it is not a guaranteed swimming or diving depth. For real-world use, follow the instructions for the exact watch model, because activity guidance differs by manufacturer and resistance can decline with age or damage.
What does a watch water-resistance rating really mean?
The number is a pressure indication, not a promise about how deep you can take the watch. ISO’s consumer explainer describes bar as the pressure unit used in practice and gives an approximate relationship of 1 bar to the pressure at 10 metres of water. That helps explain labels such as 5 bar and 50 metres, but does not make those two values a real-world depth guarantee.
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Casio explains that watches are tested against static pressure. Movement through water, a forceful impact with the surface, or other vigorous activity can create dynamic pressure beyond that test condition. A wearer’s actual exposure therefore differs from the static laboratory setup represented by the marking.
ISO’s April 2013 explainer discusses ISO 22810:2010, Horology — Water-resistant watches, as a standard detailing specifications, requirements and tests for watches marked water-resistant. It distinguishes that category from ISO 6425 diver’s watches intended for scuba diving. The explainer is dated and cites the 2010 edition; it is not confirmation of the current edition of either standard.
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Which water activities are safe for your watch?
There is no single rating chart that applies to every brand. The following are manufacturer-specific examples, not interchangeable guarantees. Consult the manual for your exact model before exposing it to water.
Casio’s activity guidance
| Casio marking | Activities listed in Casio’s guidance |
|---|---|
| No water-resistance marking | No water exposure |
| Water Resistant | Splashes and rain |
| 5 bar | Splashes, rain, bathing, washing and showering |
| 10 bar | Activities listed for 5 bar, plus swimming and snorkeling |
| 20 bar | Activities listed for 10 bar, plus free-diving without equipment |
Casio’s FAQ says its 5-bar and 10/20-bar categories should not be used for scuba or other air-tank diving. These recommendations apply to the Casio products covered by its guidance, not to every watch with the same number.
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Seiko’s activity guidance
| Seiko marking | Activities listed in Seiko’s guidance |
|---|---|
| 3 bar | Daily use such as splashes and rain |
| 5 bar | Swimming and showering |
| 10, 15 or 20 bar | Bathing and shallow diving |
| Diver’s Watch 200 metres | Scuba diving |
| Professional Diver’s Watch 1,000 metres | Saturation diving |
Seiko’s recommendations differ from Casio’s for some activities, including bathing and diving. Do not transfer one maker’s table to another watch. A non-dive rating alone does not establish that a watch is suitable for scuba diving; look for the model’s explicit diver designation and limits.
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Is an Apple Watch waterproof?
Apple describes Apple Watch as water resistant, not waterproof. Apple says Series 2 and later have a 50-metre rating under ISO 22810:2010 and are suitable for shallow-water activities such as pool or ocean swimming. In Apple’s guidance, models other than Ultra should not be used for diving, water skiing, or activities involving submersion below shallow depth or high-velocity water. Apple describes Ultra models as suitable for recreational scuba diving up to 40 metres.
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These statements are generation- and model-specific. Some band materials also have separate liquid-exposure limitations. Check the current manual for your exact watch and band rather than assuming that the 50-metre label permits every activity.
Why water resistance can change
Water resistance is not permanent. Casio says seals wear naturally with age, and that temperature extremes, solvents and cosmetics can accelerate deterioration. Seiko identifies aging gaskets and shocks that deform watch parts as factors that can affect resistance.
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After a hard impact, repair, or long period without service, ask a watchmaker or authorized service provider whether the watch should be tested before water use. The manufacturer sources do not establish a universal test interval. Casio’s FAQ recommends gasket replacement about every two or three years for the watch categories it covers; treat that as Casio’s advice, not a schedule for every watch.
How to care for a water-resistant watch
- Follow the care instructions for the exact model and its stated water-resistance category.
- After ocean-water exposure, Seiko advises rinsing the watch and drying it. Seiko also advises wiping moisture, sweat or dirt with a soft, dry cloth.
- Do not wash a Seiko watch with its crown pulled out. Seiko also advises against washing it under direct running water.
- Have the condition of seals considered after a shock or repair, or when the watch has gone a long time without service.
What to check before wearing a watch in water
- Read the exact marking and manual. Identify the manufacturer’s stated rating, standard if listed, and activity-specific limits for your model.
- Match the activity to the maker’s guidance. Rain, swimming, snorkeling, scuba and saturation diving are distinct use cases; do not infer permission for one from a broad metre value.
- Check the watch’s history and condition. Consider its age, any impact or repair, and whether its resistance has been tested or serviced.
- Check accessories separately. A band or other material may have different exposure limits from the watch case.
As Patrick Loetscher, then Secretary of ISO/TC 114 and its water-resistant watches subcommittee, put it in ISO Focus in April 2013: “With consumer protection in mind, ISO 22810:2010, Horology – Water-resistant watches, details the specifications, requirements and tests necessary for watches to be stamped ‘water-resistant’.” The key distinction for owners is that a tested marking describes resistance under specified conditions; the model’s instructions determine its intended use.
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