While not technically part of a watch’s anatomy, it is important to have a good understanding of what the phrase water resistance means and how it applies to a wristwatch. The term “waterproof” is not allowed by the Federal Trade Commission in the United States. This is because under the proper conditions, anything can leak. The phrase “waterproof” is used in almost all of the rest of the world.
A watch is generally considered water resistant if it can withstand the pressure of 30 meters (99 feet). Sometimes a watch’s water resistance is referred to in “atmospheres.” An atmosphere or “ATM” is 10 meters or 33 feet, therefore a watch that is water resistant to 3 ATMs is water resistant to 99 feet.
The Bar is a unit of pressure measurement that is essentially equivalent to an ATM. If a watch displays that it is pressure resistant to 3 Bar, it would be water resistant to 99 feet.