The grade of waterproofness is normally engraved on the casback of your watch. It is better NOT to take this grade literally; it is an standard manufacturing norm which indicates against which athmospheric pressure your watch resists and that all gaskets en seals, used to maintain the waterproofness, are conform this norm.
The more you use your watch, the quicker the gaskets and seal will change their caracteristics and loose their ability to keep your watch waterproof.
• Let have your watch tested every year.
• It’s advisable to change all gaskets & crown once every 2 years.
• After a battery swap there’s NO GUARANTEE on the waterproofness of your watch; even when your watch was watertight before. Make a test.
• Never trie to open your watch yourself.
• Never manipulate your watch under water.
• Make sure your crown is well screwed to the case before entering the water.
• After a swim in salted water, make sure to rince your watch properly with water.
• 3 ATM : Rain
• 5 ATM : Shower, swimming
• 10 ATM : Snorkeling
• 20 ATM : Diving
Don’t use your watch in the water. Only divers need a timepiece under the water. Using your watch in the shower or bath (sauna) might shorten the lifetime of your gaskets & seals. Residues of soap will stick in your bracelet and will become smelly after a while. If you really want a watch to go swimming on holiday you’d better buy a simple cheap watch just to preserve your valuable timekeeper.