It is particularly useful for professional divers to use a diving watch. This is because it can be used to measure decompression times, for example, which are essential for their survival. The watches have to meet a few requirements: They need a water resistance of at least 20 bar and must be easy to read even in the dark under water at a distance of 25 cm. In addition, it is necessary that time spans can be measured with the help of the bezel or a timer. The bezel is usually rotatable so that the beginning of a period to be measured can be marked with it. This has the benefit of not having to use pushers for the stop function, which have an increased risk of letting in water. In order for the watches to be used for diving, they are tested beforehand. Here, the shock resistance, the rate behaviour, the readability and the density at excess air pressure are examined. If all requirements are met, the watch can be called a diver's watch. The water density, for example, is checked with a leak tester that simulates a certain water pressure. However, if the water density is 20 bar, for example, the watch is subjected to a 25 % higher pressure during the test. This ensures that the watch not only has sufficient water resistance, but also long-term protection against moisture intrusion.
