Watches with the indication 'water resistant' on the back or watch face are designed to protect against water. for example during washing or washing the car. They are not designed to go swimming. Rubber seals protect the back, crown and chronograph buttons from water or damp. By hard knocks or falls the watch can be less waterproof than when purchased.
What does the term 'bar' or 'ATM' mean by waterproofing? A bar = 10 meter water pressure. 5 bar is the same as 5 ATM (atmosphere).
Scheme: water resistant depths - Water resistant - 30 meters: protection against water splashes or when washing hands. - Water resistant - 50 meters: protection against water when swimming on the surface. - Water resistant - 100 meters: protection against water when snorkeling. - Water resistant - 200 meters: protection against water when diving (not deeper than 40 meter).