Water resistance rating is typically specified in meters, bars or atm units and indicates how well a watch is sealed against water. If a watch has water resistant stamped on it then it signifies the watch conforms to the ISO standards for water resistance.
A standard water resistance rating will protect the watch during everyday activities where water is concerned such as showers, washing up etc. but prolonged submergence is not advised. A watch with a divers water resistance rating will typically be for depth of 100m and above.
Water ClockWinding Mechanism