Just about every manufacture of watches makes at least one "dive" watch. The first that comes to mind for most people is the Rolex Submariner. Most other dive watches are at least loosely based on the Sub. But even among Subs, there are all sorts of different styles. The hands on an older Tudor Sub are quite different from the hands on a modern Rolex Sub. The dials, and rotating bezels, can be different colors. And of course there's the "Sea Dweller" - the uber-Sub.
Other examples quickly come to mind - the Breitling Top-Time (James Bond's had a geiger counter built-in). The IWC Aquatimer. The Patek Philippe Nautilus. The Cartier Pasha. The Omega Seamaster. The Seiko and Casio dive watches are also right up there.
So, what makes a watch a dive watch?
Wikipedia defines a dive watch as a watch designed for underwater diving that features, as a minimum, a water resistance greater than 10 ATM, the equivalent of 100 meters (330 feet). There is an ISO standard for diver's watches (ISO 6425). These are suitable for diving with underwater breating apparatus in depths of 100 m or more; an ISO 6425 certified watch can be marked with the word "DIVER'S".
But there are thousands of watches out there that are water resistant to 100 m. Really, you could take just about any modern watch scuba diving. So what unique features make a watch a diver's watch?
Well, the ISO certification standard gives us some clues.
1) Fantastic visibility in just about all levels of light.
The ISO certification requires adequate readability at 25 cm in total darkness; an indication that the watch is running in total darkness; clearly distinguishable minute markings.
But a good diver's watch, I think, should go beyond this. It should be legible at any light. The sun's glare. The light of the moon. A dim reflection. A lot of watches are readable in complete darkness; it's when there's just a little bit of light that makes reading them difficult - your eyes adjust to absolute darkness, and become much more sensitive. Analog watches should have several different ways of reflecting light back to your eyes. The hour and minute hands should have a healthy amount of chemiluminescence. But they should also have some "mirrored" elements, and (ideally) some sections in white or other color that contrasts highly with the colour of the dial. Hour markers on the watch should be the same - ideally they should have mirrored segments, black or white segments (high contrast to the face color), and a healthy chemiluminescent dollop.
Although a diver's watch can have a face of any colour, the majority are black with white hands and markers. I think my "perfect" diver's watch will have to have this color combination, or a minor variant of it (dark blue?). Strictly an aesthetic thing, but isn't that the most important thing here? After all, it's not like I even dive!
2. Easy to read the exact time
The ISO standard states that there should be clearly distinguishable minute markings on the watch face. Makes sense to me.
3. Unidirectional bezel
The ISO standard states that there should be a unidirectional bezel, with elapsed minute markings at least every 5 minutes, and a specific marker to mark a specific minute marking.
In other words, there should be a rotating bezel. It can only rotate in one direction. So, once it's set, it can be accidentally moved, but only to tell you you have LESS air, not that you have MORE air. i.e. if you set the marker at the minute hand now, the minute markings will tell you how long you've been underwater. If the bezel gets moved accidentally, it can only be in the counterclockwise direction, which means when you see how much time you've been under water, it will seem like more, not like less, time.
I would add a few things to the ISO standard (not that I've read the ISO standard, but I'm just reading about it on Wikipedia... my apologies if these things are part of the standard already, and just not mentioned in Wikipedia). First, the specific marker should be chemiluminescent. It should also be readily visible in any light conditions. AT A MINIMUM, you should be able to read three things in any light conditions: the location of the minute hand, the location of the "12", and the location of the bezel marker.
Second, the bezel should have some kind of grip on it, so that it can be easily turned, even with gloves on.
Third, the bezel should "click" every minute (or half minute). None of this free-wheeling bezel stuff - you need a bit more accuracy than that.
Fourth, ideally, the bezel should be designed so that sand and salt won't gum it up. I don't want to have a "stuck" bezel, just because I've been in the sand or sea - that's what it's for! I'm a bit torn about whether this means that the bezel needs to be an internal bezel (like the one on some of the IWC aquatimers). With an internal bezel, you just turn a crown to turn the bezel, but the bezel is under the crystal, and is therefore protected from sand and salt. However, it does change the look of the watch a lot - I'm not sure if a "perfect" dive watch should have an internal bezel...
Finally, I'm a bit torn on whether the bezel should be one colour or two - in a lot of traditional dive watches, the first 15 minutes of the bezel are a different colour. Not sure why that is - I would understand it if we were counting down (last 15 minutes you can be underwater) but on almost all of these bezels, we're counting up. I'll have to look into the significance - now it's really staring to bother me.
4. Tough, reliable watch
The ISO certification has requirements for magnetic resistance, shock resistance, chemical resistance, strap/band solidity. It also nees an End of Life indicator on a battery powered watch, and an indicator that the watch is running. Makes sense to me. You don't want the watch falling off in the middle of the ocean. You want to know that you're not going to run out of batteries in the middle of a dive. You want to be able to glance at the watch and confirm that it's still running, and doing what it needs to do. Theoretically, you are depending on the watch for your health and safety.
Also makes sense that the watch should be able to withstand the corrosive nature of seawater.
5. Looks like a Dive watch
I think it's important for a dive watch to look the part. It should have a metal, rubber, or fabric strap. A big, easy to read, black face. A serious piece of metal on your wrist. It should be devoid of fancy features that decrease legibility - no chrono dials, preferably no date indicator (though, if you must, one with a black background). Although the quintissential dive watch (the Rolex Sub) has a cyclops magnifier for the date window, I would do without - it distorts the face, and sticks up too much (it will get banged up and scratched). This is a utilitarian watch. Oh - and I think it should have a wetsuit extension clasp if it's a metal band, or an extra-long bracelet if it's rubber or fabric. It should have a safety clasp. Big thick hands. And a screw-down crown. I'm not too fussed about fancy shmancy "helium release valves", depth guages, trip computers, or any of those things.
So this wednesday, we'll take a look at our first dive watch. And we'll look at another every Wednesday 'till I get bored and decide to look at other types of watch for a change.