The rotating bezel is the most characteristic component of a dive watch. Despite its simple function, a timepiece without timing bezel cannot be considered a real dive watch.
So what is the rotating bezel’s role in diving? Let’s find out now!
Exact timing is very important to a scuba diver because his/her oxygen supply is always limited. It’s very dangerous to not know how much time has elapsed underwater. Therefore, the rotating bezel on dive watches acts as a reminder to prevent divers from exceeding their diving time limit.
Basically, we can use the rotating bezel in two ways
Measuring elapsed time
- Rotate the bezel to point the lumed pip against the minute hand.
- The minute hand continues to move on, and the gap between it and the lumed pip indicates how much time has just passed. If the minute hand points at the 20 position on the bezel, this means you have been diving for 20 minutes.
Measuring remaining time
Scuba divers use the bezel this way more often!
- Determine your bottom time, for example, 35 minutes
- Follow this formula: 60 – bottom time (60 – 35 = 25)
- Rotate the bezel till the 25 position lines up with the minute hand
- If you did correctly, the minute hand now takes 35 minutes to reach the lumed pip’s position, the gap between them indicates your remaining bottom time, don’t overpass it.
You will notice that the first 10 – 25 minutes on the bezel are often displayed in a more detailed and highlighted way that the rest! Why? This is derived from Rolex’s design on their 1950s classic diving watches. The bezel’s highlighted first quarter is for measuring ascent time of the diver, so this area should be more detailed than the rest.
This “count-down” bezel was quite useful in military underwater tasks at that time, but it seems to be obsolete for today’s diving.
In terms of construction, there are two types of rotating bezel:
The bezel is installed under the crystal. This design gives your dive watch a dressier appearance because it looks no different to a normal dress watch at first glance. It’s usually a bidirectional bezel which can be operated through an additional crown. This type of rotating bezel is not broadly used due to some disadvantages:
- Difficult to operate: divers normally set the bezel after taking on a wet suit with diving gloves, so a small crown is too difficult for them to grip and turn single-handedly.
- Complex texture: internal bezel, which is remotely controlled, is definitely more complicated than external bezel, which can be directly operated on the watch face.
- Additional open on the watch case: A dive watch’s body should be as leak-free as possible, and the easiest way for water to get inside is through the crowns. One more crown means one more potential open on the case.
That is the type of rotating bezel that you can see on most dive watches in any price range, from affordable to luxury. In my opinion, it’s much more practical than internal bezel:
- Easy to operate single-handedly: it’s much easier to directly grip and turn the bezel edge than to remotely operate it through a small crown.
- Easy to repair or replace: an external bezel can be disassembled & installed with ease. In case you need to fix or replace your watch’s external bezel, it would cost you much less money and effort than an internal one.
Despite some inevitable shortcomings, such as getting jammed by sand and debris, or wearing out through daily use, external bezel still has many advantages over internal bezel.
Most external bezels are unidirectional (counterclockwise-rotating) due to the matter of safety. An accidental move of the bezel would change the gap between the minute hand and the lumed pip. This leads to loosing track of remaining time, and it’s safer if the bezel unexpectedly shortens the remaining time instead of lengthening it.
It’s worth noting that some diving-style timepieces still feature a bidirectional bezel, but in fact, they are just desk divers or vintage diving pieces (the old Rolex Submariner 5513, for example),a true contemporary dive watch should features a one-way rotating bezel.