Why Watches Have Rotating Bezels – And How They Work

Why Watches Have Rotating Bezels – And How They Work

The watch is the next best invention after the clock. It may come as a surprise to you, but the first watches appeared as early as the 16th century in Germany.

The watch has evolved enormously over the centuries, in line with emerging technology, dive watches were later invented.

A watch bezel is the rotating outer ring found on many dive watches. While some bezels are stationary, most rotate uni-or-bi-directional and are graduated into 60 divisions. These markings correspond to 60 minutes in an hour and allow the diver to track elapsed time underwater and calculate the remaining oxygen in their tank.

Soon after the invention of the watch, it became obvious that, since a watch was something that a person would carry around on their person wherever they went, it could be made to perform additional functions as well. It is with this in mind that rotating bezels were integrated into watches.

So, why do watches have rotating bezels? What the heck is a bezel Anyway? Let us seek the answers to these two questions, which are part of each other.

What is a Rotating Bezel?

A rotating Bezel is part of a dive watch – in fact, it is the most vital component, which distinguishes itself from regular watches. A bezel is an outer disc that is graduated into 60 divisions corresponding to 60 minutes. It can be rotated so that the zero arrow is aligned with the 12 o’clock position on the watch. The 60 divisions on the bezel mark an hour, corresponding to the time that oxygen in a standard scuba oxygen tank usually lasts.

How To Use a Watch Bezel?

Before a diver dives into the water, they position the red arrow on the bezel on the 12 o’clock position on the watch. The graduations on the bezel can either be from 0 to 60 or from 60 to 0, these markings provide the diver with a way to track the minutes that have elapsed during the dive. The remaining time left from an hour can be estimated so that the diver has sufficient oxygen to ascend back to the surface.
The diver’s underwater time, or “bottom time as it is more popularly known, is a vital statistic of any diver. This is so because after a particular time has elapsed, the body tissue begins to absorb compressed nitrogen. Once this begins to happen, the diver cannot immediately ascend but needs to wait for a period of time at a particular depth to decompress or “off-gas” the accumulated nitrogen in the body.

Due to the above reason, the diver usually follows the “120 Rule,” which states that the maximum time in minutes that a diver can spend at a particular depth is equal to 120 minus the maximum depth. Therefore, for an 80-foot dive, the diver’s bezel will show a no-decompression limit of 40 minutes.
If a diver exceeds this time, then extra time should be spent underwater as a “penalty,” depending on the depth. Divers need to ensure that enough oxygen is available to last for that particular period; this is why the first 15 to 20 minutes on a bezel are often highlighted on the bezel in another color.
This is the primary use of a standard diving bezel, but there are several types of watch bezels, including bezels that serve as tachymeters, compass for tracking world time, and much more.

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