In the watch industry, the term "water resistant" refers to the watch's ability to withstand water pressure. Stated in units of pressure such as atmospheres (ATMs), or depth such as meters, water resistance levels typically range from 3 ATM (30 meters) to 20 ATM (200 meters) and diver's watches at 200+ meters.
Technically, no watch is fully waterproof; rather, there are some watches made to handle more water pressure than others. Watches that are equipped for swimming or diving are still only water resistant up to a certain point and there is always a risk of moisture leaking into the case and getting into the movement.
Follow these standard rules of thumb for knowing the amount of water your timepiece can withstand and the necessary precautions to prevent water damage.
| Water Resistance | Suitable Use / Precautions |
| 3 ATM (30 m) | Protected against splashes from rain, hand washing, etc. Not suitable for showering or swimming. |
| 5 ATM (50 m) | Suitable for withstanding short periods of water immersion, such as light swimming. |
| 10 ATM (100 m) | Suitable for swimming, snorkelling, and other recreational water sports. |
| 20 ATM (200 m) | Suitable for high impact water sports and shallow diving. |
| Diver | Diver's watches ratings are provided by ISO 6425 |
No matter the water resistance rating, all timepieces should be regularly serviced and checked for an accurate reading of the water resistance levels. Frequent exposure to water can cause the gaskets of the watch to erode, increasing the risk of water damage.