The water resistant quality of timepieces comes in varying degrees, typically ranging from non-water resistant to 20 BAR (ATM). Outlined below are examples exposure to moisture as well as a description of the varying degrees of water resistance.
A primary factor about water resistance to keep in mind is that it is not a permanent condition. When a piece is new, it meets the specifications for water resistance as indicated on the case back. However, as the watch ages, the gaskets which seal the watch become dry and brittle diminishing its water resistant quality. Exposure to environments such as chlorinated pools, salt water or soaps from showering can accelerate drying of the gaskets. The Citizen watch company recommends, for example, that the gaskets be changed at least every 18 months to maintain the water resistant quality of your timepiece. If the watch is exposed to chlorinated pools, soaps salt water, etc. on an occasional basis, they recommend that the gaskets be changed on a yearly basis. If the watch is exposed to the previously mentioned environments on a daily basis, they recommend the gaskets be changed every six months to insure the water resistant quality.
Water resistance is measured at a static, or motionless state. As the watch is moved in water, such as from the motion of swimming, pressure is added from velocity. While you may be swimming in a pool at surface level, the watch may be experiencing forces equal to 3 BAR (ATM). Diving into a pool can cause pressures on the watch in excess of 3 BAR (ATM).
1 BAR (ATM) is equivalent to 33 feet of water pressure. Always allow a margin of safety when exposing your watch to moisture. You should never “push the limit” of the degree of water resistance. For example, if the case back of your watch states “Water Resistant to 10 ATM, you should only expose the watch to 7 or 8 ATM of pressure. This will allow a margin of safety and is especially important as the watch ages and the gaskets dry out.
Be sure the crown is completely pushed in prior to any contact with moisture. If your model is equipped with a screw-down crown, be sure it is properly closed. Do not operate the crown or any push button when the watch is wet as this may allow the entrance of moisture.
The following chart offers a general guide on degrees of water-resistance:
| Marking on watch | Accidental splashing from hand washing, perspiration, etc. | Showering, washing the car, fishing, etc. | Swimming or snorkeling | Skin diving, scuba diving | Jacuzzi, hot tub |
| “Water Resistant” | x | No | No | No | No |
| 30m | x | x | No | No | No |
| 50m | x | x | No | No | No |
| 100m | x | x | x | No | No |
| 200m or more | x | x | x | x | No |