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 is extremely impractical to constantly take your timepiece off in everyday life so that it doesn't get splashed with water, many watch wearers specifically opt for a model that has a certain level of water resistance. Water-resistant wristwatches have the advantage that their movement is protected against pressure at a certain water depth and no water can penetrate the case. The water resistance information indicates the depth to which this is the case for each model. This article sheds light on the technical background and standards for the water resistance of watches and provides tips on buying waterproof timepieces.
The most important facts in brief
Meaning of 10 ATM: A watch that is water-resistant to 10 ATM can withstand a water pressure of 10 bar under test conditions at a depth of 100 meters.
Suitability: Such a watch can be worn when washing hands, showering, bathing, swimming and snorkeling, but not when diving.
Care and maintenance: In order to maintain the water resistance of a watch for as long as possible, it should be cleaned after intensive contact with water. It is also advisable to check the seals regularly.
What does “water-resistant to 10 ATM” mean?
Watch manufacturers usually use the units meter, bar or ATM to indicate the water resistance of a product. An indication in meters directly reveals the depth to which a watch can withstand water pressure. Bar indicates the prevailing hydrostatic pressure under water. If a watch is 10 meters below the surface of the water, an overpressure of 1 bar can be expected.
The abbreviation ATM stands for atmosphere and also refers to the pressure resistance of the watch when the water surface is at rest. Here, 1 ATM corresponds to the pressure that prevails at a depth of 10 meters; 10 ATM would therefore stand for 100 meters. 1 ATM is not quite the same as 1 bar, as 1 atmosphere is converted into 1.01325 bar, but for the sake of simplicity, the values are usually used in the same way. So we can remember: 10 meters of water column = 1 bar = 1 ATM. From this follows:
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 density in relation to watches, we quickly come across the physical concept of pressure under water. With the surface of the water at rest, the absence of pressure peaks - such as those that occur when diving into the water after jumping from a 5-meter tower - and the absence of large temperature fluctuations, the water pressure acting on the watch increases by 1 bar or 1 ATM every 10 meters. In order to produce a water-resistant watch, various precautions must therefore be taken and elements integrated into the design to prevent water from penetrating the case despite the pressure. Built-in seals are common, as are a firmly screwed case back and screwed crowns with sealing rings.
Water resistance categories and standards
The water resistance of a watch is tested using a standardized test procedure. Special testing devices subject the timepieces to a test pressure (air pressure) in the laboratory. The test results are interpreted in accordance with 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 freediving 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 in order to be called a diving watch, in many cases they can withstand 30 ATM and more. This means that adventures at greater diving depths are no problem.
Practical applications and activities
In summary, this means that a water-resistant watch with an ATM value of 10 can withstand everyday stresses and strains in connection with water. Neither showering nor bathing, hand washing or swimming will damage the watch. If you are looking specifically for watches that are suitable for water sports at shallow depths, such as snorkeling, 10 ATM is theoretically also sufficient, but freedivers and scuba divers should opt for a model that offers its movement sufficient protection up to at least 20 ATM. As already mentioned, manufacturers can call their watches diver's watches if they are not only water-protected but also “submersible”, which is the case from 20 ATM according to the standard.
Care and maintenance of waterproof watches
Both splash-proof watches and diving watches must be correctly maintained and cared for so that they remain water-resistant for as long as possible. After coming into contact with water, the surface of the watches should be cleaned and the functionality of the seals checked. It is important to avoid chemical cleaning agents, which include many household cleaners, as these can attack and seriously damage the material of the seals. If the inspection reveals that there is already obvious damage, the watch should be taken directly to a specialist for servicing. Professional maintenance at regular intervals is generally recommended.
Despite the best care, a water-resistant watch will generally not remain water-resistant forever. Water resistance decreases with use over time, so that, for example, a watch that was water-resistant to 10 ATM when first purchased may only be water-resistant to 5 ATM over the years. If you wear older watches, you should keep this in mind.
Buying advice: What to look out for when buying a waterproof watch?
If you want to buy a water-resistant watch, you should pay particular attention to these criteria:
Water resistance level: What information does the manufacturer provide on water resistance (in meters or bar or ATM)?
Area of use: For what purpose is the watch being 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?
Strap: Depending on the area of use, the strap should be made of a material that will not soften or fade even with intensive contact with water.
The Royal Oak from Audemars Piguet, for example, which is water-resistant to 5 ATM or 5 bar, is suitable for beginners for whom splash protection is sufficient. Advanced, price-conscious hobby snorkelers might opt for the Seiko 5 Sports, while water sports enthusiasts with a more generous budget should choose the Rolex Yachtmaster, which is also water-resistant to 10 ATM. If you are looking for a reliable companion for deeper water, you should take a look at the robust Seamaster Diver 300 or the Seamaster Planet Ocean 6000M from Omega.
Common misunderstandings and problems
In order to clear up any misunderstandings, we would like to take this opportunity to briefly explain the exact meaning of the water resistance specifications of a wristwatch. In particular, the manufacturer's specifications in meters can be misleading for laypeople. A wristwatch that is water-resistant to 20 bar according to the manufacturer is theoretically wearable up to a water depth of 20 meters. But it all depends on the circumstances in practice!
This is because both ATM and bar refer to the water column and the prevailing pressure under water, whereby the test pressure is built up under laboratory conditions. Under certain circumstances, the actual water pressure that a watch can withstand may deviate from the indication in meters. For example, if the watch is left in the sun and you then jump into cold water, it can be assumed that the water resistance is reduced with regard to the meter indication. The same applies to dives in rough waters and numerous other scenarios that occur time and again in practice.
Popular models and manufacturers
Finally, we would like to mention a few brand watches that fit the description “water-resistant to 10 ATM” and are definitely worth a closer look:
TAG Heuer Monaco x Gulf: automatic watch with square case
TAG Heuer Carrera Caliber 16: Chronograph with date and weekday 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 second hand
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 that is worn on a daily basis should not be affected by moisture and splashing water. Models with a water resistance of 5 ATM or more can practically remain on your wrist even when showering and watches with a water resistance of up to 10 ATM can even survive a visit to the swimming pool undamaged. How water-resistant a watch needs to be in order to fully meet the expectations of its wearer depends largely on the activities for which it is worn. It should always be borne in mind that the water resistance of a watch can decrease with increasing durability. It is therefore essential to take good care of your favorite waterproof watch and have it regularly inspected by a specialist to ensure that contact with water does not damage the movement in the long term.