In addition to being far more resilient than most watches, and water-resistant to greater depths, diving watches are designed with other features specifically for deep-sea adventurers and professional divers.
Watchmakers have always taken care to fully seal watch cases, if only to protect the movement against dust and humidity in the air. However, as the wristwatch gained in popularity in the twentieth century, watches were made specifically for divers. Strategic points in terms of water-resistance are the fixing of the crystal, case back and crown. In the first two instances, heavily compressed gaskets ensure complete water-resistance. The crown, in contrast, because it is constantly being moved, requires more than just a seal. The invention of the “screw-down” crown by Hans Wilsdorf, the founder of Rolex, in 1926 made possible the first genuinely water-resistant watch. Since then diving watches have been the focus of some spectacular developments, not least because of their use by navy commando units.
Diving watches stand out for their exceptional water-resistance to 100, 300, 1,000 and even 3,000 metres. Other characteristic features are a unidirectional rotating bezel for calculating dive times, an extra-strong crystal, and fluorescent markings for visibility in murky water. Depending on their degree of technicality, they can also offer other useful functions for deep-sea explorers: for example a helium release valve, indicators of decompression stops and times, or a depth gauge. Some even sound to indicate surfacing time.