Water Resistant Watch

Water-Resistance
Whether you’re a scuba diver or just a frequent dishwasher at home, you’ll want to pay attention to the water-resistance of your watch. Water-resistance ratings are listed in certain depths, typically in meters, but the numerical depth shouldn’t be taken literally. The depth rating actually represents the results of tests performed in a lab’s pressure chamber, and not real-world sea depths.
A watch marked as water-resistant without a depth indication is designed to withstand accidental splashes of water only. Do not submerge such a watch. Higher levels of water-resistance are indicated by increasingly higher acceptable depths, usually indicated in meters.
A watch with a back that screws onto the case provides a higher degree of water-resistance. Some crowns with a winding stem actually screw into the case to further increase water-resistance.
We do not recommend swimming or diving with your watch unless it has a screw-down crown (also known as ‘screw-lock’ or ‘screw-in’ crown) and is water-resistant to at least 100 meters.
Note: Water-resistance is sometimes listed using the abbreviation ATM, which stands for “atmosphere” and 1 ATM represents 10 meters. In Europe, “bar” is often used instead of ATM.
Below are typical water-resistance ratings and their corresponding parameters for real world usage.

Depth ATM Usage
30 meters (100 feet) 3 ATM Can withstand rain and splashes of water, such as car washing and showering, but it shouldn’t be worn swimming
50 meters (165 feet) 5 ATM Suitable for swimming, as well as higher altitude sports, such as skiing and parachuting
100 meters (330 feet) 10 ATM Suitable for snorkeling, as well as swimming
200 meters (660 feet) 20 ATM Suitable for recreational scuba diving
300 meters (990 feet) 30 ATM For use when scuba diving to a depth of 30 meters for up to 2 hours
500 meters (1650 feet) 50 ATM For use when scuba diving to a depth of 50 meters for up to 2 hours

Maintaining Water-Resistance
Like everything in life, a watch’s water-resistance isn’t guaranteed forever. The gaskets or O-rings that make up the watch’s watertight seals can degrade over time, and even opening the caseback for changing the battery can affect water-resistance. To make certain that your watch will stand up to the pressure that was designed for, a watch can be tested and repaired by a service center authorized by the manufacturer. Here are some tips on maintaining your timepiece’s water-resistance.

Tips
Never submerge even the highest-rated water-resistant watch in a hot tub (or take it into a sauna), as the gaskets can lose their shape when exposed to extreme heat.  After submersion in salt water, rinse your watch with warm fresh water to help avoid corrosion.
If your watch has a screw-down crown, make sure to screw it tightly into the watch case to help prevent any chance of water getting into your timepiece.  Do not expose your watch to extreme changes of temperature.  Do not press buttons underwater.  Read your manual so you know features and resistance.

Care for a Water-Resistant Watch
It is not recommended to wear your water-resistant watch in a hot shower, sauna or hot tub. The extreme heat can cause the metal parts to expand at a different rate than the rubber gaskets. This creates small openings that can allow water droplets to penetrate the watch. Sudden temperature changes are especially harsh. Take care not to jump into a cold pool after wearing your watch in the hot tub.
After swimming or diving in salt water, immediately rinse the watch in a stream of fresh water. If your watch has a rotating bezel, turn the bezel several times while rinsing it. This will prevent salt buildup and corrosion of the bezel ring.  Leather straps can be made to be water-resistant too. Generally however, leather straps are more easily damaged by frequent exposure to water. If you are going to wear your watch while swimming, think of buying one with a metal bracelet or a rubber or nylon diver strap.