Perhaps it says it on the back of your watch. Or maybe it’s written in small text on the face.

We’re talking, of course, about a watch’s water resistance. Water is necessary for many things to run smoothly, like humans and plants. But when watches and water mix, the results can vary and lead to one unhappy — albeit busy — watchmaker.

So what is water resistance? That term, if found somewhere on your watch, means the timepiece is humidity tested and you won’t have to worry if it encounters some brief water exposure. This means if you were to get caught in a rainstorm or have some water splash up your wrist while doing the dinner dishes. It doesn’t mean the watch is guaranteed to function after swimming or showering while wearing it.

There are levels to water resistance, which just means a less expensive watch in the $20 neighborhood probably isn’t your best bet to survive a trip 30,000 leagues under the sea. The International Organization for Standardization (ISO) sets standards for water resistance and uses an atmosphere scale, where one atmosphere (or ATM) is equal to about 10 meters or roughly 30 feet below the surface.

A watch with 3 ATM (~100 feet) is suitable for everyday use, but is not suitable for swimming, whereas 5 ATM would be safe for bathing. A watch needs to be at least 10 ATM to be suitable for swimming and snorkelling, while 20 ATM is the threshold for high-impact water sports and diving. For a timepiece to be considered a diver’s watch, it needs to be water resistant to at least 100 meters below the surface.

However, for the longevity of the watch’s sake, it’s best just to take it off before entering bodies of water, pools or showers.

 

WATER RESISTANCE CHART

3 ATM, 30m, 100ft

Suitable for everyday use. Will withstand accidental splashes but not suitable for swimming.

5 ATM, 50m, 165ft

Suitable for everyday use and bathing but not suitable for swimming.

10 ATM, 100m, 330ft

Suitable for everyday use and swimming and snorkelling but NOT suitable for high board diving or sub-aqua diving.

20 ATM, 200m, 660ft

Suitable for all high impact water sports and scuba diving at depths not requiring helium gas. At these depths it is recommended to purchase a professional watch

20 – 50 ATM, 200 – 500m

Suitable for all high impact water sports, scuba diving and saturation diving.

100 ATM, 1000m

Suitable for deep sea diving and intergalactic travels.

Regardless of how your watch is rated, I tell EVERY customer to keep their watches as clean and dry as possible. I have seem far too many nice watches come into my shop badly damaged by water and rust.  In the last 4 weeks I have had 4 Rolex watches come into the shop that were rusted beyond any repair. Each customer had the same story. ” they have always worn their watch in the (pool, shower, ocean) and never had a problem before. Now suddenly their watch is full of water and not running.

    Keep this statement in mind ” It is not if your watch will leak, it is just a matter of when“!