Watch Water Resistance Explained: What You Need to Know

1. The Great Misconception: Waterproof vs. Water Resistant

The first thing every watch owner must understand is that no watch is truly "waterproof." In fact, under ISO (International Organization for Standardization) guidelines, manufacturers are actually discouraged from using the term "waterproof."

Instead, we use the term Watch Water Resistance. This is because, under enough pressure or due to the natural degradation of rubber gaskets, any watch can eventually leak. When a brand labels a watch as "water resistant," they are stating that the watch can withstand a specific amount of static pressure for a certain period in a laboratory setting.

2. Deciphering the Units: ATM, Bar, and Meters

When you see a rating on a dial or case back, it is usually expressed in one of three ways. Understanding these is the foundation of mastering Watch Water Resistance.

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  Meters (m): The most common unit, representing a theoretical depth.

  
  


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  ATM (Atmospheres): 1 ATM is the pressure of the air at sea level.

  
  


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  Bar: A unit of pressure almost equal to an atmosphere (1 Bar ≈ 0.98 ATM).

  
  

So, if your watch says 5 ATM, it is theoretically resistant to the pressure found at 50 meters of depth. However, as we will see, "theoretical" is the keyword here.