A watch can take in water through three places: the crystal, the crown and the cover. The water resistance of a watch is its ability to prevent water or even dust from entering the case. This resistance can be read on the back of the case and it is important to know how to interpret it as the degree of water-resistance varies from watch to watch. This number can be expressed in Atmospheres (ATM), Bars (BAR), Meters (m) or Feet (feet).
1 ATM or BAR = 10m = 33 feet
U-Boat Classico Automatic Watch
Water resistance is the ability of a watch to withstand pressure under water and is measured in bars or atmospheres of pressure. Water resistance is established by the ISO 2281 and ISO 6425 standards, depending on the watch.
For a watch to be recognized as water resistant, it must comply with the international standard ISO 2281. Diving watches withstand immersion to a depth of at least 100 meters and must comply with ISO 6425.
Watches are usually engraved with their water resistance, whether 30, 50, 100 or 200 meters, but this does not mean that they can be submerged to that depth of water. These numbers respond to the level of water pressure that the watches resist, which differs according to the depth, so it is always advisable to check the instruction manual for the actual water resistance of the watch recommended by the manufacturers.
It should be noted that water resistance tests are performed by watch manufacturers in laboratories, in conditions equivalent to a motionless swimmer, therefore phenomena such as sudden pressure changes or extreme temperatures, among others, are not taken into account. These variables affect water-resistance, so manufacturers cannot guarantee the water-resistance properties of the watch indefinitely. It is recommended that you visit a service center once a year to check the condition of your watch and its water-resistance.
You can check this table as a guide.
Diver watches were born in the mid-twentieth century, and became popular with the sport itself. These watches have a helium valve that prevents the watch from being damaged by pressure, among other features.
You can read more about the functions of these watches in our entry Diver and submersible watches.
