Glossary
Water resistance and ATM ratings
water resistance ATM
Water resistance ratings (ATM, bar, or meters) describe lab-tested resistance to pressure — not a blank check for swimming, showering, or diving unless the rating, crown design, and gasket condition support that use.
How to read the numbers
One ATM equals roughly 10 meters of static pressure in a lab — not the same as swimming to that depth. Common markings: 30m / 3 ATM (splash only for most), 50–100m (light swim for many modern seals if crown is secure), 200m+ (serious dive territory when the watch is designed for it). Screw-down crowns help; they are not magic if gaskets are old.
Real-world caution
Hot showers, soap, and age degrade seals. Vintage ratings are historical, not current certifications. If water use matters in your brief, we prioritize recent pressure tests and honest ratings over marketing meter numbers.
FAQ
What does 10 ATM mean?
About 100 meters of lab pressure resistance. Many 10 ATM watches handle swimming when seals are healthy — still avoid operating the crown underwater and retest after service or impacts.
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