Why is water resistance important in watches?

Whether you're showering, washing your hands, bathing, or swimming: you don't have to be a diver for the watch you wear on your wrist to come into contact with water. Because it's extremely impractical to constantly take off your timepiece in everyday life to avoid splashes of water, many watch wearers specifically opt for a model with a certain level of water resistance. Waterproof wristwatches have the advantage that their movement is protected against the pressure at a certain depth, preventing water from penetrating the case. The water resistance information reveals the depth to which this applies to each model. This article sheds light on the technical background and standards governing watch water resistance and offers tips for purchasing waterproof timepieces.

The most important things in brief

• Meaning of 10 ATM: A watch that is water resistant to 10 ATM can withstand a water pressure of 10 bar, as it exists under test conditions at a depth of 100 meters.

• Suitability: Such a watch can be worn while washing hands, showering, bathing, swimming and snorkeling, but not while diving.

• Care and maintenance: To maintain a watch's water resistance for as long as possible, it should be cleaned after intensive water exposure. It is also advisable to check the seals regularly.

What does “waterproof up to 10 ATM” mean?

Watch manufacturers typically use meters, bar, or ATM to indicate a product's water resistance. A measurement in meters directly indicates the depth to which a watch can withstand water pressure. Bar refers to the prevailing hydrostatic pressure underwater. If a watch is 10 meters below the water surface, an excess pressure of 1 bar can be expected.

The abbreviation ATM stands for atmosphere and also refers to the pressure resistance of the watch, specifically at still water. 1 ATM corresponds to the pressure at a depth of 10 meters, so 10 ATM would represent 100 meters. While 1 ATM is not exactly the same as 1 bar, since 1 atmosphere is strictly speaking converted to 1.01325 bar, for simplicity's sake, the values ​​are usually used in an adjusted manner. So, we can remember: 10 meters of water column = 1 bar = 1 ATM. This gives:

• 20 meters = 2 bar = 2 ATM

• 30 meters = 3 bar = 3 ATM

• 50 meters = 5 bar = 5 ATM

• 100 meters = 10 bar = 10 ATM

Technical basics of water resistance

If we delve a little deeper into the background of water resistance in relation to watches, we quickly come across the physical concept of underwater pressure. With a still water surface, no pressure peaks—such as those that occur when submerged after jumping from a 5-meter tower—and no large temperature fluctuations, the water pressure acting on the watch increases by 1 bar or 1 ATM every 10 meters. Therefore, to create a waterproof watch, various precautions and elements must be taken during the design process to ensure that no water penetrates the case despite the pressure. Common examples include built-in seals, a firmly screwed case back, and screw-down crowns with sealing rings.

Categories and standards of water resistance

A watch's water resistance is tested using a standardized test procedure. Special testing equipment subjects the timepieces to a test pressure (atmospheric pressure) in the laboratory. The test results are interpreted according to the applicable DIN standards:

• From 2 bar or 2 ATM: The watch is splash-proof ("water resistant") and can be worn, for example, when washing hands or in light rain

• From 5 bar or 5 ATM: The watch can be taken into the shower without hesitation

• From 10 bar or 10 ATM: The timepiece can be worn in the swimming pool and for snorkeling

• From 20 bar or 20 ATM: The watch is suitable for free diving or scuba diving at shallow depths

Many diving watches offer much more: Although they "only" have to be water-resistant to 20 atmospheres according to the DIN 8306 standard to be called a diving watch, in many cases they can withstand 30 ATM and more. This means that even adventures at greater depths are no problem.

Practical applications and activities

In summary, this means that a waterproof watch with an ATM rating of 10 can withstand everyday stresses associated with water. Neither showering nor bathing, washing your hands, or swimming will damage the watch. If you're specifically looking for watches suitable for shallow water sports, such as snorkeling, 10 ATM is theoretically sufficient, but free divers and scuba divers should opt for a model that offers adequate protection for their movement up to at least 20 ATM. As already mentioned, manufacturers are allowed to call their watches diving watches if they are not only water-resistant but also "submersible," which, according to the standard, is the case from 20 ATM onwards.

Care and maintenance of waterproof watches

Both splash-proof watches and diving watches require proper maintenance and care to ensure they remain watertight for as long as possible. After contact with water, the watches should be given a surface cleaning and checked for proper seal function. Chemical cleaning agents, including many household cleaners, should be avoided, as these can attack the seal material and cause serious damage. If obvious damage is discovered during the inspection, the watch should be taken directly to a specialist for service. Professional maintenance at regular intervals is generally recommended.

Even with the best care, a waterproof watch generally doesn't stay waterproof forever. With use, the water resistance decreases over time, so, for example, a watch that was water-resistant to 10 ATM when new may only be water-resistant to 5 ATM over time. If you wear older watches, keep this in mind.

Buying advice: What should you look for when buying a waterproof watch?

If you want to buy a waterproof watch, you should consider the following criteria:

• Water resistance level: What information does the manufacturer provide regarding water resistance (in meters, bar, or ATM)?

• Area of ​​use: For what purpose is the watch purchased (e.g. everyday companion, for swimming or diving)?

• Quality and case: How high-quality should the watch be and which materials are preferred for the case?

• Bracelet: Depending on the intended use, the bracelet should be made of a material that does not soften or fade even when exposed to intensive water.

For beginners who are satisfied with splash protection, the Royal Oak from Audemars Piguet, water-resistant to 5 ATM or 5 bar, is a good option. Advanced, price-conscious snorkelers might choose the Seiko 5 Sports , for example, while water sports enthusiasts with a more generous budget opt ​​for the Rolex Yachtmaster, which is also water-resistant to 10 ATM. Those looking for a reliable companion for greater depths should consider the robust Seamaster Diver 300 or the Seamaster Planet Ocean 6000M from Omega.

Common misunderstandings and problems

To avoid any misunderstandings, we would like to briefly explain the precise meaning of the water resistance information on a watch. Manufacturer specifications in meters can be particularly misleading for laypeople. A watch that claims to be water-resistant to 20 bar is, in theory, wearable up to a depth of 20 meters. However, it all depends on the practical circumstances!

Both ATM and bar refer to the water column and the prevailing pressure underwater, with the test pressure being developed under laboratory conditions. The actual water pressure a watch can withstand may, under certain circumstances, differ from the specified pressure in meters. For example, if the watch is left in the sun and then you jump into cold water, you can assume that the water resistance will be reduced with respect to the meter specification. The same applies to dives in choppy waters and numerous other scenarios that frequently occur in practice.

Popular models and manufacturers

Finally, we would like to name a few brand watches that fit the description "waterproof up to 10 ATM" and are definitely worth a closer look:

• TAG Heuer Monaco x Gulf : Automatic watch with square case

• TAG Heuer Carrera Calibre 16 : Chronograph with date and day display

• TAG Heuer Link: Elegant quartz watch with marbled dial

• Zenith Chronomaster Sport : Chronograph with small seconds, date and luminous indices

• Rolex Cosmograph Daytona : Chronometer with screw-down crown

• Rolex Milgauss : Magnetic field-resistant wristwatch with characteristic lightning hand

• Rolex Datejust 41 : Automatic watch with date and Roman numerals

• Rolex Sky-Dweller : Chronometer with luminous hands, date scale on the dial and small seconds

• Rolex Oyster Perpetual : Sporty steel watch with luminous indices and hands

• Omega Speedmaster 38 Co-Axial : Automatic chronograph with date display

Conclusion: The right watch for your needs

A watch worn every day should be unaffected by moisture and splashes of water. Models with a water resistance of 5 ATM and above can conveniently be left on the wrist even while showering, and watches with a water resistance of up to 10 ATM can even survive a visit to the swimming pool unscathed. How waterproof a watch needs to be in order to fully meet the wearer's expectations depends largely on the activities it is worn for. It is always important to keep in mind that a watch's water resistance can decrease over time. Therefore, it is essential to take good care of your favorite waterproof watch and have it inspected regularly by a specialist to ensure that contact with water does not cause damage to the movement in the long term.