As a SCUBA Instructor I have been teaching people how to dive and use a dive watch for more than 25 years.

When you look at a dive watch, one of the first things you will notice is the bezel surrounding the outside of the crystal. This is one of the main features that distinguishes a dive watch. The bezel is actually a timing device used to time a dive while on SCUBA.

If you try to rotate the bezel it should only rotate to the left. If it rotates both ways it is only for show and not a dive watch. True dive watches only have bezels that rotate to the left, it is called a unidirectional rotating bezel.

The bezel is numbered and marked usually at five minute intervals. Some watchmakers have included minute indicators, which I find helpful but ultimately are not completely necessary. Most bezels now are built with minute indicators at least to the 15 or 20 minute interval. I’ll cover why later down below.

History

Blancpain was the first watchmaker to use the unidirectional rotating mechanism in the early 1950’s. The bezel only rotates counterclockwise. The function of the dive watch bezel is to measure elapsed time. Rolex had introduced the rotating bezel to watches in the 1930’s, but Blancpain was the first to patent the unidirectional feature. All other manufacturers had to have theirs rotate both ways until Blancpain’s patent ran out.

So Blancpain more or less invented the dive watch we know and love today, especially as it pertains to the unidirectional bezel.

Why is it Unidirectional?

If, while diving, you accidentally bump or move the bezel you cannot accidentally increase your bottom time, you will only shorten it. This is very important, because it is bad to absorb more nitrogen in your bloodstream than you think you have and could potentially pose a problem. That’s why it only rotates to the left.

Diving 101

When you breathe air underwater your body starts to absorb more nitrogen than when you are breathing at the surface. The deeper you go, pressure is increased on the tissue in your body. The deeper you go and the longer you stay at depth the more nitrogen you absorb. So, without going down a rabbit hole and discussing nitrogen absorption, absorbing too much is bad. That’s why we time ourselves while diving. If you are really interested in this subject I encourage you to take an Open Water Scuba Diver course.

The bottom line is this needs to be closely monitored so divers don’t absorb too much nitrogen, that’s where the bezel comes in.

Bezel Operation

When diving, your dive time begins when you begin your descent from the surface. What I do and what I teach is set the bezel immediately before beginning your descent. You will rotate and align the bezel zero or arrow marker to the minute hand. Most bezels adjust in either 60 or 120 click increments so you are able to get exactly right on the minute marker.

From there you are timing your dive. Or, you can do the same thing if you are making hard boiled eggs or cooking a steak. I find I use my dive watch bezel a lot for cooking.

So you are going along on your dive and let’s say it is a dive to 45 feet and you are getting low on air at 54 minutes and are back by the dive boat. The minute you begin your ascent your dive time is over.

Earlier I mentioned that there are minute markers on the bezel to the 15 or 20 minute marker. The purpose of these is to mark either a safety stop, or a decompression stop. Both are similar in nature in that you are stopping at a predetermined depth for a predetermined amount of time.

So back to the dive, you are ascending from 45 feet to 15 feet to complete your 3 minute safety stop. When I level off at 15 feet I set my bezel zero/arrow to the minute hand again. This starts the clock counting from zero again. I sit there for three minutes and then finally ascend to the surface. This is why the first 15 or 20 minutes on the bezel usually have indicators for each minute.

This allows nitrogen to off gas from my body while still under some pressure. If I were to go to the surface immediately the off gassing would happen more rapidly and that’s where a problem could occur.

Now with the advent of the dive computer in the 1980’s most people use a computer for both non decompression diving and especially for decompression diving. However, if I am going on a shallow dive I often just use a watch and tables. And if I am using a dive computer I still use my watch as a backup. As a diver it is a tool I will never do without.

Before You Purchase a Dive Watch

OK, so you are ready to go on a dive, you have your dive watch and you are going out tomorrow. There are a few things to consider in relation to the bezel operation.

Are you going to be wearing gloves? If I’m diving in warm water the bezel operation is just as easy in the water as it is in my house. Your hands are warm, you have full tactile function and good grip with bare skin. On the other hand, if you are diving in cold water with gloves you are trying to grip the bezel with neoprene, and you may not have as much control if your hands are cold. It’s just a lot harder to grip things with cold hands.

These are considerations you need to think about before purchasing a dive watch. Look at the machining on the bezel below, it is large and easy to grip, even with neoprene gloves.

For me, I do 99% of my diving in the tropics with no gloves. However there was once a time when most of my diving was done in cold water in a drysuit. Two very different conditions that require different gear, including how big and grippy the bezel is on my dive watch.

Bezel Pip

At the zero marker on most dive watches you will notice a small dot usually filled with luminous paint. This is called the bezel pip. This is useful when you are night diving and you want to move the zero marker on the bezel to the minute hand, either when initially starting your dive, or initiating a safety stop.

Other Uses

When not diving I find myself using the bezel for timing all sorts of things. As mentioned previously I use it most of the time for cooking, but you find yourself timing all sorts of things.

I suppose I could use my smartphone for this, but I’ve been wearing a dive watch for 30 years. I’m just used to setting the bezel.

So there you have it. Now you know how to use the bezel on your dive watch. This article is a little technical, so if something isn’t clear please let me know through my contact page so I can update the blog post.