Even in case you have no plans to wear your watch during diving trips, swimming in hotel pools, or during something more practical activities like washing your car or doing dishes, the water resistance of a watch is something to keep in mind when buying a watch.
The fact that your watch or watch manual indicates it has a water resistance of 30m/ 3ATM or even 50m/5ATM does not mean you can dive respectively 30 or 50 meters deep with it. Water resistance is a bit more complex than that, unfortunately. This article should shed some light on the subject.
Here’s a little chart to show you the general accepted guidelines for water resistance indicated for a watch and what it truly means:
|< 50 meters||No swimming, diving, snorkelling, surfing or other activities in water|
|50 meters||Swimming only|
|100 meters||Swimming and other water sports except diving, snorkelling, etc.|
|200 meters||Swimming, diving (not scuba diving!)|
|> 300 meters||Swimming, diving, scuba-diving|
Then, of course, there are watches that have an extreme water resistance like 500 meters, 1000 meters, 2000 meters, or even more (e.g. 3,900 / 12,800ft Sea-Dweller DeepSea model from Rolex). These watches are suitable for saturation diving, a specific diving technique that allows professional divers to work at great depths (with reduced risk of suffering from decompression sickness).
So, why does a watch indicate 30 meters or 50 meters when it’s actually not suitable for diving? Well, it is a guideline that indicates what your watch is capable of handling when it comes to water, moisture, and – yes – dust. Is the watch sealed, does it have a sealed crown (diving watches most of the time have a screw-down crown or other technical solution to keep it closed safely), and a screwed case back or even a monobloc-case?
If your watch has been properly sealed using gaskets – and that’s about it – it will probably have a 30m rating. You can wear it when it rains outside, it will be dust free (no dust will enter through the crown or caseback), but take it off when doing the dishes. To withstand water, and pressure, there is more to it than just gaskets.
The watch case must be able to withstand pressure and the effect of (salt) water to prevent it from corroding. Although you’d say precious metals would be very suitable, they are also expensive and relatively soft (pressure and shocks). So stainless steel and titanium are often used for diving watches. The construction of the case is also of importance, as said, some professional diving watches use monobloc-cases (Seiko Marinemaster 300 or the vintage Omega Seamaster PloProf 600M) or are installed with a helium-release-valve.
The helium-release-valve is of use for saturation divers, as the helium that got into the watch case under high pressure needs to get out before the watch returns to normal pressure conditions again. If not, the difference in pressure inside and outside the watch is too high and can result in a blown-off crystal and other damage as a result of that. The Rolex Sea-Dweller and Omega Seamaster 300M have a helium-release-vale for example, for which Rolex uses an automatic helium valve and Omega uses an extra crown (located at 10 o’clock) to operate the helium valve.
To prevent the watch from taking in water (or dust and moisture in general), the crown also plays an important role. Already in the 1920s, the screw-down crown was invented (Rolex wasn’t the first, but did patent it in the mid-1920s). Rolex, with its Oyster case, was able to make name and fame with Mercedes Gleitze swimming the English Channel with a Rolex Oyster on her wrist in 1927. Omega was also very early with water resistant and diving watches, like the Omega Marine watch. This was long before these brands had their Submariner and Seamaster models (1950s). You will also find brands with technical or at least typical solutions to ‘lock’ the winding crow. Panerai, with its long history of Italian Navy watches, used a lever to push the crown firmly on the case. Brands like U-Boat and Visconti have similar unconventional methods to ensure the crown is tightened.
Some diving watches also have ‘complications’ on board, such as a chronograph. In 1993, the Omega Seamaster Professional 300M Chronograph was the first model to have pushers that could be used under water. A lot of chronographs have pushers that can’t be used under water and actually need to be unscrewed before use (above the surface), like the Audemars Piguet Royal Oak Chronograph or Rolex Daytona. If the use of a chronograph in the water is important to you, check if the watch is capable of doing so.
These days, diving watches are also a matter of style and most (big) brands have a collection of diver’s watches in their catalogue. Although most of these watches are indeed capable of being used as a diving watch, some brands take it very seriously and take it one step further: to obtain an official certification as a diver’s watch. German brand Sinn Spezialuhren is famous for its “form follows function” concept and innovations regarding anti-fogging, water resistance, material hardness, and so on. Sinn was the first company to comply with European diving equipment standards and the first to have their diving watches certified for pressure resistance, water resistance, and resistance to fogging.
So, even if you are not looking for a watch to accompany you on some recreational diving trips but do want to use it during the occasional swim on your holiday destination, take the level of water resistance of your watch very seriously.
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