Dive Watches in Depth: A Dive Watch FAQ

Dive Watches in Depth: A Dive Watch FAQ
Dive Watches in Depth: A Dive Watch FAQ

The engineering used in good dive watches is fascinating and you don’t have to be a diver to love them. As a matter of fact, people love wearing tool watches like dive watches, pilot watches, survival watches, even though they don’t do any of those activities, even as hobbies.

However, we will take a closer look at frequently asked questions about dive watches. In the end, whether you are a professional diver or not, or whether you have a dive watch right now on your wrist or are willing to get one soon or later, you will be glad you learned more about them. Get ready to dive down on some deep technical information and interesting facts, although we will try to keep it as simple as possible. 

Why is a dive watch important?

Primarily, a dive watch allows the wearer to keep track of time underwater. It helps you to monitor elapsed time underwater and understand how much air you have left in your breathing tank. In addition, you can also dive knowing you are following the dive safety guideline to eventually perform decompression stops and measure your surface time before a second dive (The latter is necessary to allow the body to re-oxygenate). For, example, if your first dive was 20 minutes, you should rest on the surface for at least 35-40 minutes. 

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As for decompression stops, in case you don’t know yet, are performed when the diver ascends to the surface when he/she has been diving beyond the threshold of 40 meters (130 feet). It avoids decompression sickness (pressure injury) caused by a large amount of nitrogen (absorbed from the air tank) on the body tissues that are not dissolved yet. 

To perform these actions when only equipped with a dive watch, you will also need a decompression table and a depth gauge. However, do not forget to enjoy your time underwater as there are no-stop dive times that allow you to be a sea dweller for even hours before you absorb too much nitrogen. Some no-stop dive times:

DepthTime Left
10 meters (32 feet) 3 hours 40 minutes
16 meters (52 feet)      1 hour 12 minutes
20 meters (65 feet)                    45 minutes
25 meters (82 feet)                    29 minutes
30 meters (98 feet)                  20 minutes
35 meters (114 feet)                 14 minutes
40 meters (131feet)                   9 minutes
42 meters (138 feet)8 minutes

How water resistant should a dive watch be?

According to the International Standards Organization (ISO), a dive watch must be at least 100 meters water resistant. For a dive watch to obtain the designation as 100 meters water resistant it needs to be first tested for water resistance in the laboratory with testing machines.

However,  the watch is being tested in an artificial environment, without taking into account extreme temperatures, aging of the case, and pressure changes as the diver descends and ascends. This load of imponderables causes the watch brands to give a somewhat enormous pad of security with the goal that watches lovers won’t consider them liable if their watches leak.

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What is ISO 6425 Standard for diving watches?

ISO pulls together specifications from standardization organizations in 165 countries to create a common source of standards for information security, medical devices, and understandably dive watches. ISO 6425 was first introduced in 1982 and was revised in 2018. The latest framework states that a dive watch must withstand diving at depths of at least 100 meters. It should be equipped with a measuring system to indicate the elapsed time (bezel or integrated stopwatch feature) and must be visible in the dark. Furthermore, a dive watch must also be resistant to shocks and low and high temperatures. 

What is a diving depth gauge and how are they different from dive watches?

A diving depth gauge is a pressure gauge that is used to measure the depth below the free surface in water. It is used for practical purposes such as diving and along with the diving watch and a dive table, the frogman can easily make certain calculations like the elapsed time underwater and plan decompression stops depending on the depth he has been plunging. A depth gauge only measures the depth below the free surface while a dive watch measures the elapsed time underwater. 

US Marine diver with a diving Casio G-Shock watch and 

an analog depth gauge.

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Blancpain X Fathoms – A dive watch with a built-in depth gauge.

What is the difference between a dive watch and a dive computer?

With the rise of dive computers in the late 1980s, a slow death began for dive watches. With a dive computer on their wrists, divers no longer needed to perform calculations underwater as it could provide real-time data for depth, elapsed time, surface time, and decompression stops. 

Yes, the technology is quite amazing and since this moment, dive watches were doomed. While a dive watch completes its function with the help of a depth gauge and a decompression table, a dive computer comes with built-in sensors that indicate current and max. depth, dive time, and even water temperature. Some models also calculate the amount of air left in a tank. 

What is the helium escape valve on a dive watch?

A helium escape valve also called a helium release valve, is a feature found on diving watches and is designed to allow the watch to release pressure when helium makes its way into it. See, helium molecules are among the smallest of all (even water molecules), and under extended periods of high pressure, the molecules find their way past the seals of a watch. 

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The watch crystal can then pop up due to extreme pressure underwater causing the diver to be left there with a not-working watch, so vital to complete the necessary calculations. To avoid that from happening, the valve released the built-up gasses trapped inside, as the watch returns to a neutral pressure environment. It is most important for commercial divers, like saturation divers, whose work requires staying for days or weeks underwater performing different tasks like construction, inspection, or maintenance.

During this time, their dive watch accumulates pressure for the trapped helium molecules and is released prior to the decompression process. Courtesy of the helium escape valve. 

Does a dive watch needs a helium escape valve?

Not necessarily. It depends on your occupation underwater while wearing the watch. If you are a saturation diver, you don’t use the usual breathing gas underwater (21% oxygen/ 79% Nitrogen) as nitrogen narcosis can be a real issue, especially when you are using air-supplied devices for prolonged periods of time. Instead, professional divers use a Trimix fill cylinder (21% oxygen, 35% helium, and 44% nitrogen) or Heliox (a mixture of helium and oxygen with 0% nitrogen).

As you can understand, if you are not working underwater for prolonged periods of time, you will not necessarily need a dive watch with a helium escape valve as there is no helium. If yes, it is highly important to have one!

Interesting Fact- Scuba is an acronym for Self Contained Underwater Breathing Apparatus

How do rotating bezels on dive watches work?

It is easier to do it than explain it, that’s for sure. Simply put, a rotating bezel on a dive watch is used to measure the elapsed time underwater to avoid decompression. So how to use the rotating bezel on a dive watch?

  1. When you are about to descent, you start rotating the bezel counterclockwise (uni-directional 60-minute bezel) until you have aligned the minute hand with the main marker (dive marker). 
  2. As time passes, you can look at the minute hand pointing at the bezel your dive time. 
  3. As you are about to ascent, you again align the main marker to the minute hand current position. You can now properly time your ascent, and take the necessary decompression stop.

Many dive watches have 15 one-minute markers with 5-minute increments leading to 60 minutes like Omega Seamaster Planet Ocean. There are many other dive watches as well that come with 60-minute markers like the Omega Seamaster Coaxial. This does not compromise or change the process of timekeeping as is more about the overall aesthetics. 

Are dive watches used by divers today?

With the start of commercial and recreational scuba diving in the mid-50s, dive watches were created as a response to the market. Dive watches dominated the underworld until the 1980s when the dive computer came into play. It wiped out the necessity of a dive watch with its user interface that allowed the frogman to enjoy the underworld while the computer does the calculations and sends vital information promptly. 

Now, as with every piece of equipment, dive computers can sometimes fail. Note that these are rare cases, however, it is always a good idea to have a genuine dive watch with you. One per wrist. 

What are the properties of professional dive watches?

  • ISO 6425 (preferable)
  • At least 100 meters of water resistance
  • Legible dial, (luminous hands & markers, hand-dial contrast)
  • Measuring system (bezel or integrated stopwatch feature)
  • Durable strap (rubber or stainless steel)
  • Helium escape valve and screw-down crown (As aforementioned, the helium escape valve is necessary only if you are a saturation diver. On the other hand, the screw-down crown is a must-have for every dive watch. It aids in water resistance thanks to crown gaskets which create an air-tight seal when screwed in.)