What is the water resistance of a watch? If a watch is water resistant, you will usually see WATER RESISTANT on the case back, some watches will show it on the dial as well. But if a watch has no water resistant, then you’d better keep your watch away from water. There are 3ATM, 5ATM, 10 ATM, 20ATM and 30ATM water resistance, sometimes measure it with BAR. Let’s see what is ATM and BAR. Every 10 meters of underwater depth increases the pressure by 1 bar, and when the pressure inside and outside of the case is uneven, the watch is prone to bursting. Therefore, watch manufacturers use the “pressure value” to test the water resistance of a watch, and use the pressure resistance value (unit BAR or ATM) to express the depth of water resistance. 1 atmosphere is equal to 10 meters of water depth, 1 ATM = 1.01325 BAR, which can be estimated as 1BAR = 1 ATM = 10 meters of water depth.