Everything You Need To Know About Dive Watches

The old proverb “time and tide wait for no man” is never truer than when you are in said tide. Actually, you don’t have to be in tidal waters; any time you are submerged dans l’eau you need to be acutely aware of time. Whether leisurely enjoying a non-decompression dive at 30 meters or working at 2000ft in an atmospheric suit as a commercial diver, you can’t afford to lose track of time. Where now there are highly sophisticated wrist-mounted dive computers, for many years divers needed a waterproof watch. A dive watch is now considered a luxury accessory, but there was a time when these objects were a matter of life or death and a tool of the trade; hence the term ‘tool watch’.

Sealed

The most obvious attribute for a dive watch is waterproofness. There is little point having a watch that you rely on in the water if it can’t cope with being submerged regularly. The most famous example of the waterproof case is the Oyster case, designed by Rolex and Tudor founder Hans Wilsdorf. I’ve written about this watch here, so I won’t cover old ground, but I believe it’s fair to say that Wilsdorf created the most successful commercial dive watch in the world, with the Submariner. Rolex was beaten to market in 1953, however, by Blancpain with its Fifty Fathoms dive watch. The Fifty Fathoms was the brainchild of a French Navy Captain, who led a combat swimmer unit. He took his design originally to French watchmaker Lip who declined to make the watch, with Blancpain eventually agreeing to manufacture it. 

Where others had failed, both Blancpain and Rolex were able to commercially produce reliable watches that could be taken to a depth of 100 metres (fifty fathoms is approximately 91 meters, but you get the jist). Recreational divers rarely dive deeper than 40 meters and so the 100 meter depth rating, that seems to be standard, is more than adequate. By the mid-1950s Rolex had managed to get their watches waterproof to a depth of 200m with the reference 6200 and other brands followed (wet)suit. The system, developed by Wilsdorf, used a screw-down caseback and winding crown, with a pressure fit bezel. It’s a waterproofing system that has never been beaten and is the backbone of the recent Deepsea Challenge that can withstand the pressure and remain impervious to the elements at 11km deep…essentially the bottom of the earth’s ocean. Oh, and in line with the ISO standard for dive watches, Rolex over-test the watches by another 25%!

Seen

Ever wondered why the hands on a dive watch are so big, even ‘too’ big sometimes? Legibility is a key issue, especially when diving in dark or murky conditions. In the early days of dive watches, brands used radium on the dials. I would recommend testing an aforementioned Rolex 6200 with a Geiger counter as not being suitable for the faint of heart. The bold Arabic numerals and large mercedes-pattern hands needed a lot of luminous material and therefore a lot of radium. As the years went by, technological and scientific advancements were made and harmless substances were developed for luminous material, such as the industry standard Super LumiNova that is used on many of today’s watches.

The three most important readings on a dive watch are the bezel, the hour markers on the dial and the hands. Sticking with Rolex, very quickly after its release the Submariner had its original pencil-style hands replaced with the mercedes-pattern hands. These made the hour and minute hands more easily distinguishable and combined with the bold luminous hour plots and lume filled pearl on the bezel, that have become the archetype for the dive watch, were easily readable in most conditions. 

Timed

The critical part of a dive watch is the rotating bezel. The basic premise is that one moves the lume dot to line up with the minute hand of the watch, thus allowing the diver to accurately measure elapsed time. This is why the luminous pearl or dot on the bezel is so important. In the early years, these bezels were bi-directional and held in position by a washer spring.  Now for safety and security reasons, dive watches that comply with the ISO standard must have a bezel that is “protected against inadvertent handling”. This is most commonly achieved by using a unidirectional bezel system that operates on a ratchet system. The bezel also needs markers at every five minute point. 

Before the advent of wrist mounted dive computers, watches would be paired with a depth gauge, also worn on the wrist, that would allow the diver to monitor his depth. If diving below 40 metres, a diver would need to undertake periodic pauses in the ascent to the surface, to avoid decompression sickness. Along with the watch and depth gauge, a set of waterproof printed tables or charts that showed how long an ascent was needed depending on the depths that the diver went to was also a key piece of equipment. In 1967 Doxa unveiled the Sub 300T Professional, a watch that featured a new, patented rotating bezel. The Doxa bezel had two sections, the usual elapsed time ring and a second that combined was known as the No Decompression Bezel. The outer ring allowed a quick reading on the allowed time for each depth without the need to pause to decompress on the way back up to the surface. 

Released

Some divers go deeper than others and those working at significant depths for prolonged periods breathe a helium and oxygen mix called Heliox. Helium particles are tiny compared with those of water. The seals on a dive watch that are perfectly capable of keeping water out of a watch case, can’t prevent helium entering the case when a diver is in a saturation environment. During the diver’s decompression, the helium is in a big hurry to leave the case and builds up quicker than the seals can allow them to leave with the result being that the crystal will pop off the watch. There are two types of gas escape valve, automatic and manual. The automatic valve, as seen on Rolex Seadwellers and the Breitling Superocean allows the gas to escape via a one-way system that sits flush within the case side, usually the opposite side to the winding crown. The manual escape valve, as used on the Omega Seamaster, is a screw-down crown that when unscrewed allows the gas out, whilst still being waterproof.

Collected

Of all collectible sports watches, the dive watch is one of the most sought-after by collectors. Having long been in the shadows of the chronograph, the dive watch is having its moment. Some of the most notable of collectable dive watches are those issued to the military. Omega SM300 and Rolex Submariners issued to British forces command staggering prices at auction, often fetching 20 to 30 times the price of a non-issued version. Tudors used by the French Navy and Blancpain Fifty-Fathoms badged as “Tornek-Rayvilles” used by US Marines are also highly prized. But whether you want to laze in the bath or take a watch down to the bottom of the Mariana Trench, you can find a watch that will suit your purpose and your wallet.