Diving watches are among the most popular type of watches these days, but what makes a diving watch a diving watch is not too clear. In general, a unidirectional 60-minute bezel seems to be mandatory, as well as a reasonable water resistance. Here we are already on a slippery slope, because what is reasonable for a diving watch? 100 meters, 300 meters, or perhaps even more?
It would be great if there were a standard to which we could compare all diving watches, and fortunately, there is. The International Organization for Standards, better known by its acronym ISO, developed one. Known as ISO 6425, the current version has been active since 1996 and incorporates a lot of the requirements that Blancpain used to develop the Fifty Fathoms. Watches that meet the requirements setout by this standard may officiall mark their watch as “diver’s watch”
The exact list of requirements is long and technical, so we will only give a brief overview of the most important. The first one is probably quite surprising, as the minimum water resistant depth for ISO 6425 is “only” 100 meters. While it is not uncommon these days for diving watches to have a water resistance a ten-fold of that, the fact of the matter is that even nuclear submarines don’t dive that deep. ISO 6425 does require that each watch is tested to 125% of its depth rating prior to being sold, so there is quite a safety margin in this.
Further is a unidirectional bezel mandatory, and must the hour and minute hand, marker on the bezel, as well as the running second’s hand, be visible in the dark at a distance of 25 cm from your eyes. ISO 6425 also requires that watches meet the criteria set out in ISO 1413 (shock resistance) as well as ISO 764, which refers to the antimagnetic properties of the watch. Furthermore, the watches also have to meet criteria for salt water resistance, thermal shock resistance, and that is not even all….
It is the testing of each and every watch that makes it that many watch manufacturers do not sell their watches as ISO 6425 certified, as it can be cumbersome, expensive and don’t always add anything. Rolex never claimed that their watches meet ISO 6425 requirements, yet the Submariner and Sea-Dweller have been the watch of choice of professional divers for decades. While an ISO 6425 certification means that you have a very capable diving watch around your wrist, it doesn’t mean that a watch that doesn’t have it is necessary less competent. The question also remains is how many people truly need an ISO 6425 certified watch, but the answer to that is very personal.