What do watch water resistance ratings mean?
A water resistance rating is a pressure test, not a safe diving depth. 30 m means splash resistant; you want 100 m to swim and 200 m to dive.
Why the depth isn't the depth
Ratings in metres, bar or ATM describe the static pressure a watch passed in a lab, under the ISO 22810 standard: 1 ATM or 1 bar is roughly 10 metres. But swimming, diving in and jets of water add dynamic pressure, and gaskets age. So a 30 m watch isn't safe 30 m down; it's safe in the rain.
Dive watches are tested to a stricter standard, ISO 6425, which adds a safety margin and requirements like a timing bezel and legibility in the dark.
Keeping it water resistant
Screw down the crown and never press chronograph pushers underwater unless they're rated for it. Avoid hot showers and saunas, which make gaskets expand and contract. Have water resistance tested every year or two, and after any battery change or service.
What each rating means
| Rating | Good for | Watches |
|---|---|---|
| 30 m (3 ATM) | Splashes and rain. Take it off to swim. | 71 |
| 50 m (5 ATM) | Hand-washing, showers, light swimming. | 90 |
| 100 m (10 ATM) | Swimming and snorkeling. | 160 |
| 200 m (20 ATM) | Recreational scuba diving. | 109 |
| 300 m (30 ATM) | Serious diving; most professional dive watches start here. | 56 |
Current watches in our catalog, which is weighted to popular enthusiast models. Watch counts cover each rating up to the next one.
Questions
- Can I swim with a 50m watch?
- Light swimming is usually fine, but most brands recommend 100 m for regular swimming and snorkeling.
- What does 5 ATM mean?
- That the watch passed a pressure test of 5 atmospheres, roughly 50 metres. It's fine for rain and hand-washing and light swimming, not diving.