Performance feature of a watch
An essential feature by which the practical value of today's wristwatches is determined, is its water resistance.
To test this, the watch is exposed at the manufacturer to the pressure, which is indicated on the dial or the caseback. The test pressure is measured in atmospheres (atm) or in meters (m) of water column. This means that the manufacturer guarantees that the watch in the shipped status withstands the specified static test pressure.
These are two aspects to be considered
From these two points above, the following restrictions apply
For dive watches a water resistance as high as possible is an obvious condition - beneath a number of other additional requirements, such as the measurability of the dive time.
Since Rolex patented the waterproof Oyster in 1926 the usual precaution to achieve the highest possible water resistance is a screw-in crown. In chronographs there accordingly must also be screwed pushers, which can lead to a rather complicated operation. Meanwhile, there are also other modern sealing techniques to achieve a comparable density of up to several hundred meters depth without screwing the crown .