Waterproof watches: understanding and choosing wisely
Water resistance is an essential criterion when buying a watch, especially for those who want to wear it every day without worrying about water. However, there is a lot of confusion surrounding water resistance indications. What does a “50m” or “10 ATM” watch really mean? Can you really dive with a watch marked 100m?
What is waterproofness in watchmaking?
The water resistance of a watch refers to its ability to prevent liquids or dust from entering the case. Contrary to popular belief, a watch that says "50m" does not mean that it can be submerged 50 meters under water.
Water resistance is expressed in ATM (atmospheres), meters (m) or feet (ft), which refer to the static pressure exerted on the watch. This pressure does not take into account water movement, temperature variations or impacts that can increase the actual pressure.
Units of measurement for waterproofness
ATM (Atmospheres)
ATM is a unit of pressure that roughly corresponds to the pressure exerted by a 10-meter-high column of water. Thus, a watch marked 3 ATM can withstand a pressure equivalent to static immersion at 30 meters , but this does not mean that it can be submerged to this depth.
Meters and feet
The indication in meters or feet can be misleading, because it does not correspond to the actual depth of use. For example, 50m of water resistance does not allow swimming with the watch , because this indication is based on static laboratory tests.
Water Resistant vs Waterproof
- Water Resistant : Indicates resistance to water under certain conditions, without guaranteeing absolute waterproofing.
- Waterproof : A term rarely used in watchmaking, because no watch is completely waterproof in all conditions.
Waterproofing Levels and Recommended Uses Table
| Indication | Actual use |
|---|---|
| No indication | No water protection |
| 3 ATM / 30m | Splash proof, hand wash, rain proof |
| 5 ATM / 50m | Cold shower possible, but swimming not recommended |
| 10 ATM / 100m | Swimming and water sports without deep diving |
| 20 ATM / 200m | Snorkeling and freediving |
| 30 ATM / 300m and more | Scuba diving with bottles |
Factors influencing tightness
Sealing gaskets
Rubber or silicone gaskets prevent water from entering the housing. Over time, these gaskets wear out and need to be replaced.
The screw-down crown
A screw-down crown provides much better protection against water than a conventional crown. It is essential for diving watches.
The bottom of the box
A screw-down caseback improves water resistance compared to a clip-on caseback. This is something to consider when choosing a waterproof watch.
Wear and shock
A watch may lose its water resistance after shock or prolonged exposure to extreme temperatures. It is recommended to have it checked regularly.
Testing and maintaining the water resistance of your watch
Verification in watchmaking
Watchmakers perform air or water pressure tests to ensure that a watch maintains its water resistance.
Good maintenance practices
- Have the seal checked every 2 to 5 years.
- Rinse the watch with clean water after exposure to seawater or chlorine.
- Never handle the crown underwater.
- Avoid hot showers and sudden temperature changes.
Mistakes to avoid
- Believing that a watch marked 50m can be used for diving.
- Do not screw the crown back in after adjustment.
- Thinking that a waterproof watch is permanently protected without maintenance.
- Use a waterproof watch under high water pressure (powerful jets, jumping into water).
Choosing a watch according to its use
- Daily use : 3 ATM to 5 ATM is sufficient.
- Occasional water activities : 10 ATM is recommended.
- Water sports and diving : choose 20 ATM and above, with ISO 6425 certification.
Frequently Asked Questions
How do I know if my watch is still waterproof?
Only a test carried out by a watchmaker can confirm this. Water resistance decreases over time.
Can you swim with a 50m watch?
No, because the 50m indication corresponds to a static pressure. Dynamic immersion increases the pressure undergone by the watch.
Why can a waterproof watch get wet?
Wear of the seals, an impact, or incorrect screwing of the crown can compromise the watertightness.
Is a waterproof watch protected against dust?
Yes, but waterproofing does not always guarantee protection against fine dust.
