Seals leak at certain rates, no seal can be made absolutely perfect. The seals in devices that have time limits are poor seals and will start leaking on immersion and after the time limit has passed, an amount of water will have bypassed the seal and it will no longer be protected. read more
Gaskets begin to erode and break down over time, diminishing the water resistance of a watch. It is important to test your watch once a year for water resistance. Any competent watch maker should have the necessary basic equipment to test the watch - the cost involved should be minimal. read more
However, water resistance does not mean you should swim or shower with your watch on. Water is the biggest enemy of a watch. If you go swimming or play sports, you should have your watch checked for an accurate reading of its water resistance levels every year. read more