A watch marked “200 m” or “20 bar” is not automatically safe to wear at that depth—or suitable for scuba diving. The marking relates to pressure-resistance testing; for scuba, look for the manufacturer’s explicit diver-watch designation and follow the instructions for that exact model.
What does a water-resistance rating actually mean?
A water-resistance marking describes a watch’s resistance to pressure under specified test conditions. ISO 22810:2010 sets requirements and test methods for water-resistant watches and identifies the markings manufacturers may apply; ISO lists the 2010 edition as reviewed and confirmed in 2021. ISO 22810:2010
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The number is not a literal-depth guarantee. Casio explains that metre indications represent test pressure, while movement in water can create dynamic pressure. Actual resistance also depends on the condition of the watch’s seals and components. Casio’s water-resistance guidance
Is 20 bar the same as 200 meters?
They are commonly paired pressure and depth indications: Citizen explains 1 bar as equivalent to 1 atmosphere and a water depth of 10 m. That conversion is an explanatory equivalence, not a promise that a watch marked 20 bar can be used at 200 m in real conditions. Citizen’s water-resistance guidance
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Can you scuba dive with a 200 m watch?
Only if the manufacturer identifies that exact model as a diver’s watch and its instructions permit the intended diving. A general water-resistant marking—even “200 m” or “20 bar”—does not establish scuba suitability. Grand Seiko, for example, describes “DIVER’S WATCH 200m” as suitable for scuba diving, while its 10 or 20 BAR category is described for diving without an air cylinder. Those are manufacturer-specific categories, not universal rules for every watch with the same number. Grand Seiko’s water-resistance guidance
A diver’s watch is not defined by its pressure marking alone. Citizen says its diver’s watches meet ISO 6425 requirements, which include criteria beyond water resistance, such as readability, magnetic resistance, shock resistance and strap strength. Citizen’s Diver’s Watches
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What water resistance do you need for swimming or diving?
There is no reliable one-size-fits-all conversion from a watch’s printed rating to an activity. Manufacturers provide activity guidance for their own watches, and those instructions should take priority over a generic chart. Seiko’s table, for example, assigns activities to individual markings; Grand Seiko distinguishes its diver’s-watch category from its categories for diving without an air cylinder. Seiko’s water-resistance guidance · Grand Seiko’s water-resistance guidance
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Before using a watch in water, check its case or dial marking, the manual’s permitted activities, and the watch’s service condition. For scuba or other specialized diving, rely on an explicit manufacturer designation and any limits in the model’s instructions—not just a depth number.
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How to compare water-resistance ratings
- Read the exact marking. Note whether the watch says “DIVER’S WATCH” or only gives a pressure or depth figure.
- Check the manufacturer’s designation. Look in the model’s manual or official product documentation for a diver-watch classification and any named standard, such as ISO 6425.
- Match the instructions to the activity. Confirm whether the manufacturer permits swimming, diving without an air cylinder, scuba diving or other intended use. Do not infer permission from a rating alone.
- Consider condition and service. An older watch, or one that has suffered an impact, may no longer have its original resistance.
Why water resistance can change
Water resistance is not permanent. Seiko warns that ageing gaskets or deformation caused by accidental shock can affect resistance. Casio also notes that seals wear naturally and recommends periodic gasket replacement in its general guidance. Service recommendations vary, so use the exact model’s manual or ask an authorized service provider rather than applying one interval to every watch. Seiko’s water-resistance guidance · Casio’s water-resistance guidance
After seawater exposure
Seiko advises rinsing the watch with fresh water and drying it with a soft cloth after ocean-water exposure. Do not wash it with the crown pulled out. Follow the care instructions for the specific model. Seiko’s water-resistance guidance
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