Guide
Water Resistance Guide
What the numbers on a case back mean, what they don't promise, and how to keep water out. Your watch's own rating and the manufacturer's instructions always come first.
Common ratings at a glance
| Rating | Often described by makers as suitable for | Not generally intended for |
|---|---|---|
| 3 ATM / 30 m | Splashes, rain and hand-washing. | Swimming, showering or bathing. |
| 5 ATM / 50 m | Brief contact with water; some makers allow light swimming. | Diving, or high-pressure water such as jets. |
| 10 ATM / 100 m | Swimming and snorkelling, per many manufacturers. | Scuba diving, unless the maker says otherwise. |
| 20 ATM / 200 m | Swimming and snorkelling; dive-style watches meeting ISO 6425 may be marked “Diver’s 200 m” for scuba use. | Any depth or situation indefinitely, or use without regular checks. |
Typical descriptions only. Manufacturers word their guidance differently for each model.
What a rating means, and doesn't
- It's a lab pressure test. A new watch passed a static pressure test equivalent to that depth. Swimming strokes, jumping in, water jets and temperature changes are different conditions.
- It describes the watch when tested. Seals and gaskets age, dry out and compress over time, so resistance can fall without any visible sign.
- Knocks matter. An impact can disturb the crystal, case back or crown seals.
- The crown must be closed. Push it fully in, and screw it down if it screws, before contact with water. Never operate the crown or pushers underwater unless the manufacturer says you can.
- Servicing matters. After a battery change or any case opening, the seals should be checked and the watch pressure tested if you rely on its rating.
Questions
Does 30 m mean I can dive to 30 metres?
No. The figure reflects a static pressure test in a lab, not a safe diving depth. Real use adds movement, temperature changes and impacts that increase stress on the seals.
Can I shower or use a sauna with my watch?
Steam, heat and soap can affect seals and gaskets even on highly rated watches. Many manufacturers advise against it; check yours.
My watch was rated 100 m when new. Is it still?
Not necessarily. Seals age, and knocks or opening the case back can affect them. A pressure test is the way to check current water resistance.
When should I have it pressure tested?
When a battery is changed or the case is opened, after a knock, before diving, or as your manufacturer recommends. There’s no single interval for every watch.
What does “water resistant” without a number mean?
Under ISO 22810 it generally indicates basic resistance to splashes. Treat it cautiously and check the manual.
More: Watch care & tips · Watch Manuals Directoryto check your model's exact guidance.