Decoding Watch Water Resistance: A Comprehensive Guide to Terminology


Wearing a wristwatch isn’t just about style; it’s also about functionality and durability. In a world where adventures can lead us anywhere, understanding water resistance and making the right choice when purchasing a watch is crucial. The terminology used to describe water resistance can often be confusing, leaving many watch enthusiasts unsure of which watch would suit their needs. In this comprehensive guide, we break down the key watch water resistance terminology, enabling you to make informed choices when selecting a timepiece that can withstand life’s watery challenges.

1. Water Resistance Ratings Unveiled ATM vs. Metres:

Both metres and atmospheric pressure (ATM) express water resistance, so what’s the difference?

When you see a number expressed in metres like 30m, 50m, 100m, etc. this common labeling refers to a watch’s ability to withstand water pressure to a specified measured depth. However, it’s important to note that these ratings aren’t necessarily indicative of diving depth. For instance, a 30m water-resistant watch is suitable for everyday activities like hand washing, but not for swimming or diving.

In a watchmaker’s studio under tightly controlled conditions, a pressure testing machine measures ATM. The 3 ATM, 5 ATM, 10 ATM grading system indicates the water-resistant ratings. 1 ATM is approximately equal to 10 meters of water pressure. Thus, a watch labelled 5 ATM can endure water pressure equivalent to 50 metres.

citizen-BJ8057-09X-promaster-diver-ecozilla-khaki-polyurethane-strap-mens-watch-image2. Diving Deeper: ISO 6425 Standards

ISO 6425 is an international standard specifically for diver’s watches. These watches are tested under rigorous conditions to ensure they can withstand the demands of underwater exploration. Look for terms such as “Diver’s 100m,” indicating the watch meets ISO 6425 standards for diving. Water resistance for diver’s watches starts from 100m (330ft) or 10ATM, but for serious diving with breathing equipment, you should look for watches tested from 200m (660ft) or 20ATM and up.

3.  Watch Water Resistance: Clearing the Confusion

The use of both ATM and metres can be perplexing. Keep in mind that while both convey water resistance, ATM is a simplified rating often used for casual or fashion watches, whereas metres provide a more precise measure of pressure endurance. If in doubt, stick to metres for a clearer understanding.

4. Seals, Gaskets, and Crowns: Defending Against Water

Screw-Down Crown: This type of crown screws into the case, creating a watertight seal. It’s common in watches with a water resistance of more than 30 metres/3ATM to prevent water from seeping into the case through the crown. You can see whether the crown on your watch is screwed down, by trying to turn it to move the hands. If the hands move freely when you turn the crown, it hasn’t got a thread. If however (before the hands can be moved) you need to push down and unscrew it until it pops out slightly, then you have a screw down crown.

Gaskets and Seals: These are essential rubber or silicone components that form a barrier against water intrusion. Look for watches with multiple gaskets around the case back and crown for enhanced water resistance.

Herbelin Newport watch

5. Beyond Splashes: Understanding Depth Ratings

30m (100ft) 3ATM: Suitable for everyday activities like hand washing and light rain. Not recommended for swimming or diving.

50m (165ft) 5ATM: Can withstand brief water exposure like swimming in shallow water. Not designed for snorkeling or diving.

100m (330ft) 10ATM: Suitable for swimming, snorkeling, and light recreational diving.

200m (660ft) 20ATM: Appropriate for more serious diving activities, including scuba diving.

300m (1000ft) 30ATM and Beyond: Professional-grade diver’s watches designed for extensive deep-sea exploration.

6. Why Has my Watch Leaked?

So you’ve done your research and bought the right watch, but it’s now got water damage. What has gone wrong?

User error: Have you left your crown out without screwing it down tightly when you last changed the time? A watchmaker should examine any water damage, and it’s better to do so sooner rather than later! The longer you leave it, the more damage could potentially occur.

Wear and tear: have your gaskets or seals perished? Regular servicing from a reputable watchmaker can largely help avoid this. Has your watch got a cracked glass or a small dent just big enough for condensation to get in? If your watch experiences even a minor impact, it’s worth having it checked before you expose it to water again.

Professional error: were the gaskets and seals checked or replaced the last time the caseback was opened?  Was it professionally re-sealed? Amateur handling of your watch (for example when changing the battery) can invalidate its water resistance, so returning it to the original supplier or manufacturer for this is often advised.

Elliot Brown 101-A10-R06 Holton

Watch Water Resistance Guide: Conclusion

Deciphering watch water resistance terminology is the key to ensuring your timepiece can handle water-related scenarios without compromising its functionality. By understanding the ratings, standards, and components that contribute to water resistance, you can confidently choose a watch that complements your lifestyle, whether you’re diving into the depths or simply navigating through life’s unexpected wet encounters. We hope our Guide to Watch Water Resistance is informative and remember, a watch that can brave watery challenges is a true companion in every adventure.