Article written by Alexander – Founder and Owner of swissdiverswatches.com
This blog answers the following questions:
- What is a Divers Watch?
- What is the ISO-6425 international standard?
- What do the various water resistance levels actually mean?
- What is a “unidirectional bezel”?
- How does the bezel work?
(Image By Alan Warner of the US Navy)
What is a Divers Watch?
There are particular features that set divers watches apart from other watches.
The standards for what exactly constitutes a divers watch is regulated and defined by ISO-6425 – this is the international standard for divers watches. Only watches that are officially, formally and technically ISO-6425 certified, are considered to be full-fledged divers watches.
In order for a watch to be qualified to be called a divers watch, the watch needs to be water resistant down to 330 feet/100 meters minimum.
According to the ISO-6425 international standard, divers watches are tested under 125% of the formally and officially rated water pressure. This means that if a divers watch has a 200 meter rating, it has to withstand a water pressure of 250 meters, and if a divers watch has a 300 meter rating, it has to withstand a water pressure of 375 meters. The water resistance is measured in feet (ft), meters (m) or bars (bar).
Time Controller And Additional Functions:
A divers watch must also feature a time controller – usually a unidirectional bezel with which you can measure for how many minutes you’ve been under water. The indexes of the dial must be luminescent in the dark, and the timepiece must have a solid band, anti-magnetic properties and shock resistance.
In the images below you see examples of Swiss Divers Watches:
Swiss Divers Watches are made of high quality stainless steel to withstand the corrosive effect of seawater. Divers watches can also be made of other materials, such as gold, titanium, ceramic and cermet.
In the picture below you see an example of a clasp of a Divers Watch.
In the picture below you see an example of a diver’s extension which is used to adapt and adjust the size of the bracelet in order to facilitate wearing the Divers Watch over a diving suit sleeve.
Swiss Divers Watches need to be equipped with a water resistant screw-down crown such as the one displayed in the example below:
A Swiss Divers Watch needs to be equipped with a luminescent dial in order to facilitate reading the time underwater. The dial is of course luminescent outside the water as well.
Some Swiss Divers Watches are water resistant at 200 meters:
Others at 300 meters:
Others at 600 meters:
And others at 3900 meters:
Most divers watches though have a water resistance which is considerably less than 1000 meters. The typical range of water resistance is usually between 200 meters and 500 meters. A water resistance which is less than 200 meters or more than 500 meters is unusual.
There are of course dress and sports watches with a minimum water resistance of 330 feet/100 meters – and yes indeed, you will find them at this website as well, but technically speaking they aren’t full-fledged divers watches. Dress and sports watches with a 330 feet/100 meter water resistance are suitable for swimming and snorkeling but not diving.
What is the ISO-6425 international standard?
“ISO” stands for “International Organization for Standardization“.
The standards for what exactly constitutes a divers watch is regulated and defined by ISO-6425 – this is the international standard for divers watches.
In order for a watch to be qualified to be called a divers watch, the watch needs to be water resistant at 330 feet/100 meters minimum, and must be equipped with a timer in order to measure for how long the diver has been under water.
According to the ISO-6425 international standard, divers watches are tested under 125% of the formally and officially rated water pressure. This means that if a divers watch has a 200 meter rating, it has to withstand a water pressure of 250 meters, and if a divers watch has a 300 meter rating, it has to withstand a water pressure of 375 meters.
Only watches that are officially, formally and technically ISO-6425 certified, are considered to be full-fledged divers watches.
What do the various water resistance levels actually mean?
The water resistance of a divers watch is measured in, and based on, the watch being in a strictly stationary position, and not when the watch is in motion.
For example: if a divers watch is water resistant down to 300 meters/1000 feet, it means that the water resistance of the watch has been tested in a stationary position. When you’re diving and the watch is in motion, the water resistance of the watch is considerably less than the water resistance indicated on the dial.
The fact that a watch’s water resistance level is measured in meters, feet, or ATM (atmospheres) can indeed be confusing.
Many people might believe that a watch which is 30 meters water resistant (which is well below the minimum requirement for a divers watch!) can withstand diving to a depth of 30 meters. This however is incorrect.
Below I will clarify what applies to the different levels of water resistance:
- < 30 meters/98 feet: The watch shouldn’t be exposed to water at all.
- 30-50 meters/98 feet-164 feet: The watch can withstand splashes of water.
- 100 meters/330 feet: You can go showering, bathing, and swimming with the watch.
- < 200 meters/656 feet: You can go snorkeling, and diving with the watch.
While the watch is underwater: Regardless of the water protection, you should never unscrew or open the crown of the watch, or push any buttons, because the water will penetrate the pressure protected casing, and the water will seep into the watch.
What is a “unidirectional bezel”?
This denomination is commonly used concerning divers watches. A divers watch has typically a “bezel” – a ring shaped object that surrounds the sapphire crystal. We can call it the “frame” that surrounds the dial. You can turn or rotate the bezel in a counterclockwise direction. On most divers watches, you can only turn the bezel in one direction. That’s why it’s called “unidirectional bezel”.
In the picture below you see an example of a bezel. The purpose of using the bezel is to determine at what exact moment you have dived into the water, and exactly how many minutes you’ve been underwater. The reason why most divers watches use a unidirectional bezel is because the diver might accidentally nudge the watch and the bezel underwater, and that might change the position of the bezel. Instead of believing that you have more time of oxygen underwater than you actually have, it’s better to believe that you have less time, and therefore you will head quicker for the surface. The unidirectional bezel is meant to protect the diver’s life.
In the image below you see another example of a Swiss Divers Watch equipped with a unidirectional bezel:
How does the bezel work?
Take a look at your watch. What time is it? Where’s the minute hand at this moment? Turn the bezel in the counterclockwise direction until the main marker or “zero” points at the minute hand. This represents the time you dived into the water. By reading the marker or the “zero” you can determine for how long you’ve been underwater. In the picture below, the unidirectional bezel has been turned in an anti-clockwise direction, where the white arrow marker on the right is aligned with the minute hand and marks the moment the diver entered the water – in this case 8:15.
If you have any comments or questions please drop them below and I’ll be happy to answer them!
Article written by Alexander – Founder and Owner of swissdiverswatches.com
This post is very informative and engaging. As someone who has always been interested in watches, I never really knew the specifics of what makes a watch suitable for diving until I read your post.
I’m glad you find the post useful Anna.
Thanks – this is very helpful. After a bit of web work, I determined that it’s their Carlos Coste Limited Edition Mark II, released in 2007. I’ve also determined that they’re hard to find on the market, though there are a couple out there. Any thoughts as to what a fair price for a used one in good condition would be?
Ebay and Chrono 24, who are both selling used watches, have several Oris Aquis divers watches available on their sites. They sell dozens if not hundreds of different variations of the Oris Aquis, and the prices indicated on their sites should give you a good idea of what a fair price range should be.
On Chrono 24, for Oris Aquis watches in general (not specifically Carlos Coste Limited Edition Mark II), the price range is $1000-$3000.
I did find specifically the Oris Aquis Carlos Coste Limited Edition Mark II recently auctioned at Ebay, and the price for that timepiece was slightly below $2000.
Keep looking until you find the watch.
I wish you the best of luck!
Hi, Alexander. I eventually found the Oris on a site called Chrono Duo, in the UK. Wearing it now, and enjoying it immensely.
I’m glad you found a watch that you truly enjoy.
What is the watch in the second picture – black face, gold or yellow luminous markings, just below the words “in the pictures below you see examples of Swiss diving watches”
I should say the second watch pictured on this page, which appears right under the heading “In the images below, you see examples of Swiss Diver Watches” – it’s a close up shot of only a portion of the watch.
Hi Bill and a very warm welcome to swissdiverswatches.com.
The image is indeed a close up shot. It’s supposed to be an extreme divers watch called Oris Aquis Chronograph. It has a water resistance of 50 bar/500 meters.