All about water resistance in a watch

Watch water resistance refers to a watch's ability to withstand exposure to water at various depths. This is an important feature for watches and applies not only to those designed for diving, swimming, or other water-based activities, but to dress watches. Water resistance is achieved through a combination of design elements, including: seals and gaskets that prevent water from entering the watch case, a screw down crown is also an example of this; a robust case design that can withstand water pressure; specialised materials, such as stainless steel or titanium, that are resistant to corrosion.

You may have noticed that some watches feature a label indicating the ATM (Atmospheres) rating. ATM is a unit of measurement that represents the amount of pressure a watch can withstand. In the context of watch water resistance, ATM is equivalent to the following depths:

• 1 ATM = 10 meters (33 feet)

• 3 ATM = 30 meters (100 feet)

• 5 ATM = 50 meters (165 feet)

And so on. The ATM rating provides a standardised way to express a watch's water resistance capabilities.

To determine if your watch is water resistant, check the following:

• The watch's case back or dial may state a water resistance rating (e.g., "30M" or “3ATM”).

• The watch's documentation or manufacturer's website may provide information on its water resistance capabilities.

• Look for a screw-down crown or a crown with a gasket seal, which are common features of water-resistant watches.

Here's a breakdown of the various levels of water resistance, including their corresponding ATM ratings, humidity levels, and use cases:

3 Bars / 30 Meters / 3 ATM / 100 Feet

This is the minimum rating for a watch. Below 3 Bar, the watch has no water resistance. At 3 Bars, the watch can withstand everyday humidity and occasional exposure to rain or snow. The following use cases may apply:

• Suitable for daily wear in non-aquatic environments

  • Can withstand accidental exposure to water (e.g., washing hands)

  • Not recommended for swimming, diving, or prolonged exposure to water

5 Bars / 50 Meters / 5 ATM / 165 Feet

A watch rated to 5 Bars can withstand moderate humidity and exposure to water in everyday situations and is recommended for:

• Suitable for daily wear in aquatic environments (e.g., swimming pools, beaches)

• Can withstand exposure to water while swimming or snorkeling

• Not recommended for diving or high-pressure water activities

10 Bars / 100 Meters / 10 ATM / 330 Feet

A watch rated to 10 Bars can withstand high humidity and prolonged exposure to water. Its use cases are:

• Suitable for diving and snorkelling in shallow waters

• Can withstand exposure to water while surfing, kayaking, or engaging in other water sports

• Not recommended for deep-sea diving or extreme water pressure activities

20 Bars / 200 Meters / 20 ATM / 660 Feet

• A watch rated to 20 Bars can withstand extremely high humidity and prolonged exposure to water under pressure and be used for:

  • Suitable for deep-sea diving and extreme water sports

  • Can withstand exposure to water while scuba diving or engaging in other high-pressure water activities

  • Recommended for professional divers and individuals who require extreme water resistance

30 Bars / 300 Meters / 30 ATM / 1,000 Feet

A watch with this rating can withstand extremely high humidity and prolonged exposure to water under extreme pressure and can be used for:

• Suitable for extreme deep-sea diving and specialized water activities

• Can withstand exposure to water while engaging in high-risk water activities

• Recommended for professional divers and individuals who require extreme water resistance in extreme environments

50 Bars / 500 Meters / 50 ATM / 1,640 Feet

A watch with a 50 Bar rating is designed for extreme underwater activities, such as deep-sea diving. These watches can withstand humidity levels of up to 100% and are suitable for:

• Deep-sea diving

• Underwater exploration

• High-impact water sports

60 Bars / 600 Meters / 60 ATM / 2,000 Feet

A watch with a 60 Bar rating is designed for the most extreme underwater activities, such as saturation diving. These watches can withstand humidity levels of up to 100% and are suitable for:

• Saturation diving

• Underwater construction

• Extreme underwater exploration

100 Bars / 1,000 Meters / 100 ATM / 3,300 Feet and higher

A watch with a 100 Bar rating is designed for the most extreme and specialised underwater activities, such as deep-sea submersible operations. These watches can withstand humidity levels of up to 100% and are suitable for:

• Deep-sea submersible operations

• Underwater scientific research

• Extreme underwater engineering

• Some watches may feature a helium escape valve, which is a requirement for saturation diving, where the watch and wearer lives in a nitrogen enriched pressurised environment for extended periods of time

Though these are the general guidelines for usage. However, in day to day use, we caution you to be on the safe side, and generally go one level down in activity for which the watch is rated to. This is because the watch is only tested to these specifications at the factory when the watch is new. Or when it returns for service. The gaskets and seals do deteriorate with time, and this will compromise the water resistance rating. Also, it is important that when you send the watch for service, you insist that the watchmaker changes the gaskets after opening the case, and does a test each time.

Also be particularly careful, even for watches with high depth rating when using in showers. The water jet under pressure may be directly pointed at the seals. In addition, the warm soapy water has a lower surface tension than cooler fresh water. This enables easier ingress of water through the seals.  

In conclusion, watch water resistance is a critical feature that ensures the timepiece can withstand various levels of humidity and water pressure. Understanding the different levels of water resistance and their corresponding uses can help you choose the right watch for your needs.