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Water-resistance ratings are one of the most misunderstood specs in watches. The numbers don’t mean quite what they seem, so here’s a clear, practical guide to what each rating really allows.
The ratings aren’t literal depths
A “30m” rating doesn’t mean you can dive 30 metres. The figures come from static pressure tests in a lab, not real-world swimming, where movement adds significant pressure. Treat ratings as a guide to splash and immersion resistance, not diving depth.
What each rating allows in practice
30m: splashes and rain only. 50m: light swimming. 100m: swimming and snorkeling. 200m and above: serious water sports and diving.
Mind the crown
Water resistance only holds if the crown is fully pushed in or screwed down. An unsecured crown can let water in regardless of the rating.
Seals age
Gaskets degrade over time, so a watch’s water resistance isn’t permanent. If you swim with your watch, have the seals tested every couple of years.
The bottom line
Match the rating to your activity, keep the crown secured, and test seals periodically. Do that and you’ll avoid the most common — and costly — water damage.
Frequently Asked Questions
Can I swim with a 50m watch?
Light swimming is generally fine with 50m, but for regular swimming and snorkeling, 100m or more is safer.
Why can’t I shower with my watch?
Hot water and steam can degrade gaskets and the temperature swings can compromise seals, so it’s best to keep watches away from showers.
Does water resistance last forever?
No — gaskets age and seals can fail over time, so water resistance should be tested periodically, especially before water activities.
Features Writer
Daniel Cho
Daniel writes about watch design, collecting and the culture around horology, with a soft spot for tool watches and honest value.
