A Timex WR50M refers to any wrist watch manufactured by Timex that has water resistance up to 50 meters. The “WR” stands for “water resistant.”
Timex makes a large number of watches that all have the feature of being water resistant up to 50 meters. It is important to note that the term “water resistant” does not mean that users should swim with the watch on. The measurement is simply a way of gauging how much water pressure the watch resists before it breaks or becomes damaged. Water resistant is not the same as waterproof, and no watch is actually 100 percent waterproof.
Small gaskets inside of the Timex watch prevent water from getting into the watch through a seal. The only way to be sure a watch survives in the long term is to not dive with it at all. Watches eventually succumb to water pressure through enough repetition of pressure. Most gaskets in watches are designed more to resist accidents such as water splashes or rain storms. Generally, diving in water up to the recommended depth on a Timex watch is safe for the watch, but it is still best to avoid doing this more than is necessary.