Glossary

ATM (Atmosphere) is a unit used to measure water resistance in watches. This unit indicates the watch's ability to withstand exposure to water without allowing water to enter its internal components and cause damage.

The concept of water resistance is particularly important for diving watches, as they are designed to endure the pressures they encounter during diving activities. Water resistance is usually measured in meters or ATM (Atmospheres), with each unit representing the level of pressure the watch can withstand without allowing water to enter. 

For example, a watch rated as water-resistant to 50 meters doesn’t mean it can handle the pressure at a depth of 50 meters underwater. It just means the watch can resist water entering it when exposed to things like splashes, rain, or brief submersion in water. Which means the watch is suitable for daily use, but for diving, you’d need a watch with a higher rating, like 100 meters or more. Keep in mind that over time, the water resistance can weaken, so it's important to be careful.