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Delving into diving watch lexicon

Dernière mise à jour : 13 janv. 2021

Diving watches have long captivated both underwater professionals and watch enthusiasts. These must-have pieces are full of technical features. And we invite you to discover the most important ones in this little glossary!

Screw-down crown

A threaded or fluted button located on the outside of the case, this single crown is turned to wind the watch or set the time. Water resistance is improved when the crown is screwed in. Invented in 1926 by Rolex founder Hans Wilsdorf, the screw-down crown protects the timepiece during the most extreme underwater situations.

Water resistance

Water resistance refers to how well a timepiece holds up under water. To be part of the prestigious diving watch family, a timepiece must be water resistant to at least 100 metres. There are high-performance diving watches on the market that can descend to a depth well beyond this distance, even though it is rare for divers to do so. It should be noted that this information refers to the pressure felt at a depth of 100 metres when stopped (i.e. 10 bar). Nevertheless, pressure increases considerably when the diver is moving. Therefore, it is not necessary to reach a depth of 100 metres to encounter a pressure of 10 bar.

Power reserve indicator

To ensure that it continues to function, a diving watch must have a system that constantly indicates that the movement is running properly. On a diving watch, this information is usually displayed via a coloured central hand that is visible in the dark.


Readability is a crucial feature of a diving watch. To ensure that they can be read in the dark, modern specialist timepieces have a luminescent coating. Most watch manufacturers use the photoluminescent material called “Super-LumiNova®”.

Unidirectional rotating bezel

A unidirectional rotating bezel is a rotable outer ring surrounding the dial. It is used to accurately calculate immersion time and decompression stops. As its name suggests, it can only be turned in one direction, thus preventing any mishap. Hence, accidently manipulating the bezel will not present a danger, since it will only indicate that the diver has less air or decompression time (rather than more).

Helium escape valve

Heliox is a mixture of helium and oxygen used for deep diving. However, helium is able to diffuse into the watch case, causing damage when it accumulates. A helium escape valve was created in 1967 to protect diving watches during saturation and decompression phases. Its purpose is to release helium atoms from inside the case when the internal pressure becomes too high.

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