The rotatable bezel is one of the most obvious elements for dive watches. Although it is just one of many parts, a “diving watch” without a rotating bezel does not count as a real dive watch.
What makes the rotating bezel so important for dive watch?
Oxygen supply is the most important thing to divers. However, it is hard to see how many oxygens left in the oxygen tank. Because of that, divers need use time to calculate the remaining oxygen.
Normally, there are two using ways for the rotating bezel:
1. Divers can use the dive watches' bezel to measure time passed.
First, you need rotate bezel's 12 o'clock to the minute hand position. After a while, you can count the minutes between the bezel's 12 o'clock and minute hand. For example, a diver adjusts the bezel at 3:15 and get back at 3:45. It means the diver have been diving for 30 minutes.
2. Divers can use the dive watches' bezel to measure remaining time.
First, you need to know your bottom time, for example, 35 minutes. After that, you can follow this simple 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.