The Dive Watch - Everything You Need To Know

Going In-Depth With History’s Most Popular & Impactful Tool Watch

Despite the relative lack of popularity of scuba diving, the dive watch prevails as one of the most popular categories in watchmaking while also claiming several of history’s most recognizable designs including the Rolex Submariner, Omega Seamaster, and Blancpain Fifty Fathoms. Watches intended for diving have also been worn by a variety of sketchy individuals at the forefront of history-shaping events including the pioneering Panerai models utilized by the commando frogmen of the Italian Decima Flottiglia MAS in WWII, Doxa Subs on the wrists of Jacques Cousteau and his team as they pioneered underwater filmmaking, and even a modern Rolex Submariner worn by a US Navy SEAL on the raid that killed Usama bin Laden back in 2011.

(Photo Credit: W.O.E./James Rupley)

What Is A Dive Watch?

With all of that being said, we all have a general idea of what a dive watch is and does, but what exactly constitutes a dive watch? Which functions, formats, or capabilities are essential, and which are marketing fluff? In this Dispatch, backed by my experience as a commercial diver and professional watch nerd, we’ll go in-depth with the anatomy of a dive watch, presenting the key elements that add up to a competent dive timer whether or not you intend to use the watch for its intended purpose. An elapsed time bezel is also great for grilling steaks.

What Is Water Resistance?

In 2019, a custom Omega Ultra Deep descended to Challenger Deep, the ocean’s deepest point, strapped to the outside of Victor Vescovo’s submersible, Limiting Factor. (Photo Credit: Omega)

Let’s get the obvious out of the way. A dive watch is only as good as its ability to resist the sometimes massive pressures and constant risk of flooding encountered in the undersea environment. Most dive watches achieve their water resistance with screwed sealing surfaces and gaskets which are necessary because the pressure at depth can be enormous. For every foot of depth encountered by a watch in seawater, .445 pounds of pressure is applied per square inch. Divers are historically bad at math so the equation for calculating pressure on the fly is typically expressed as “half the depth” meaning that if you’re diving to a relatively pedestrian 100 feet, your watch will encounter approximately 50 (or exactly 44.5) pounds per square inch of pressure, enough to make the water really want to get inside your watch. The deeper you go, the tougher it gets for your watch’s tender insides to stay dry.

Therefore, the vast majority of watches intended for diving are rated to at least 200 meters, but many are rated to more extreme depths including 3,900 meters (12,800 feet) for the Rolex Deepsea or an even more obnoxious 6,000 meters (20,000 feet) for the Omega Planet Ocean Ultra Deep.

A 100-meter-rated watch like the Casio AE1200WH World Time is typically fine for casual scuba diving. (Photo Credit: Benjamin Lowry)

Can I Wear My Watch Underwater?

While we’re here, let’s quickly dispel a couple of common myths. I wouldn’t take a 30 or 50-meter-rated watch diving on purpose, but a watch rated to 100 meters is often fine for casual scuba diving assuming it’s relatively new and/or has been pressure tested recently. As a disclaimer, there is still an element of risk. 100 meters is a rating, not a promise of a watch's ability to dive to that depth, and the majority of 100-meter-rated watches haven't been tested in water during production. That said, modern watches are generally more capable than you'd think, and I’ve worn several 100-meter watches including the Seiko 5 Sports SSK001 and Casio AE1200WH for shallow diving profiles without issues. For what it’s worth, the ISO 6425 standard for a “professional” dive watch that we’ll get to in a bit only requires 100 meters of water resistance.

In most cases, 200 meters of water resistance is more than you could ever need. (Photo Credit: W.O.E./James Rupley)

For whoever is already typing something in all caps about “dynamic” pressure saying you need a watch rated to 200 meters to go to the pool because more pressure is applied as you move your arm and watch through the water, stop. It is technically true that a watch in motion underwater experiences more pressure than it would if it were static, but many nerds who are good at math have calculated the change as minute, the equivalent of a fraction of a foot to a few feet of depth in many instances, and functionally insignificant as it relates to the water resistance rating of your watch.

Measuring Elapsed Time

(Photo Credit: W.O.E./James Rupley)

Another crucial element of any good dive watch is its ability to manage elapsed time, a function typically utilized to track “bottom time” (defined by the US Navy as the elapsed time from when you leave the surface until you begin your ascent) but also shorter periods including safety or decompression stops. In the days before diving computers, this capability  was the single most important job carried out by the dive watch, with the bottom time being used in conjunction with a diver’s maximum depth in calculating a diver’s decompression profile. Today, this important work is usually carried out by a diving computer, but being able to measure elapsed time is still a core aspect of what constitutes a dive watch.

Typically, managing elapsed time is carried out with a rotating bezel measuring from zero to 60 minutes that is typically unidirectional, meaning it can only be accidentally rotated to express less bottom time as opposed to more, which could land a diver in proverbial hot water concerning their gas supply or profile. In many cases, dive bezels are also marked with finer one-minute intervals for the first fifteen minutes. You’ll hear different theories as to why, but I have always understood it was to precisely measure smaller amounts of time whether for decompression stops or individual legs of underwater swims in navigation scenarios.

A U.S. Navy Explosive Ordnance Disposal (EOD) Technician wearing a G-Shock DW6900. (Photo Credit: US Navy)

To be clear, elapsed time measurement by no means needs to take place by way of an external bezel. Still standard issue for US Navy Divers and amphibious special operators, a G-Shock’s stopwatch function is amazing for this task, as are certain internal bezels as long as they don’t utilize a screw-down crown in their operation. Diving chronographs can also be used, but the additional pushers often increase the potential water ingress and wouldn’t be my first choice. There are exceptions to every rule, but generally speaking, fewer case openings in your dive watch is a good thing.

Legibility

For great dive watch dials less is often more. (Photo Credit: W.O.E./James Rupley)

After water resistance and being able to track elapsed time, another central pillar in any good dive watch design is a dial and handset that is legible in all conditions including total darkness. For the dial and hands, high contrast and simple geometric shapes seem to work best. Examples like the Rolex Submariner, Seiko 6309, Benrus Type I, Tudor Snowflake, Omega Seamaster 300, and Blancpain Fifty Fathoms all have designs that have stood the test of time utilizing white luminescent indices and hands in simple geometric forms over a black or navy blue primary dial surface.

The best dive watch dials are equally visible day or night. (Photo Credit: James Rupley)

In the arena of legibility, being straightforward and even leaning into minimalism is a good thing. Lasting bright luminescent material is also important as is the ability to quickly orient the dial in total darkness or murky underwater environments. Having luminescent material on the bezel at least at twelve but preferably also elsewhere is also key as the importance of measuring elapsed time doesn’t disappear in the dark.

Despite breaking some of the design guidelines listed here, some dial designs just work. (Photo Credit: Brock Stevens)

There are exceptions to the monochromatic less-is-more rule including the orange “Professional” dial on Doxa Sub models as well as the busier display on the Marathon GSAR, both of which are excellent and highly legible underwater, but the concepts of simple geometric forms and high contrast are great places to start. For further proof of capability, always look to military dive watch designs for a trustworthy indicator of subsea utility. Military supply officers don’t care how cool you look at Red Bar, they just want the cheapest thing that will get the job done.

Straps & Bracelets

(Photo Credit: W.O.E./James Rupley)

While it may seem secondary compared to the watch itself, any great dive watch is only as good as its ability to stay on the wrist. To start, the idea that any dive watch not secured by a pull-through strap is destined for total loss following spring bar failure is overblown, but straightforward nylon straps do provide an additional measure of security while also being inexpensive and convenient for use over a wide range of different exposure suits.

After pull-through straps, I would argue a bracelet with solid end links is the next most secure method of attachment but here, we have to take into consideration the potential need for or quality of the clasp or extension system required to fit over your diving suit of choice. Rolex’s Glidelock and Tudor’s T-Fit are among the most refined, but more attainable folding extensions from brands like Seiko get the job done just as well. Many rubber straps are also great but are at least theoretically less secure compared to the aforementioned options.

For the ultimate in security, it’s tough to beat fixed lugs and a nylon pull-through strap. (Photo Credit: W.O.E./James Rupley)

Different types of spring bars and lug formats also make a difference where security is concerned. Watches like the Tudor Pelagos FXD or CWC’s collection of military watches utilize fixed lug bars that add a heightened level of peace of mind. If your watch has drilled lugs, you can use shoulderless spring bars that also decrease the likelihood of an underwater “oh shit” moment no matter what type of strap is being used. In any case, the decision about what kind of strap to pair with your dive watch should be taken almost as seriously as the watch itself, as it’s mighty hard to tell the time on a watch that’s rapidly sinking away from you into the ocean’s murky depths.

ISO 6425 Standard

The ISO 6425-rated Citizen Aqualand on a recent dive in Lake Michigan. (Photo Credit: Matt Ludvigson)

It’s not a be-all-end-all, but it’s important to also recognize the ISO 6425 standard, a benchmark for dive watches and an informative set of specifications and testing procedures laid out by the International Organization for Standardization starting in 1982. At its core, ISO 6425 describes, “…watches designed to withstand diving in water at depths of at least 100 m and equipped with a secured measuring system to indicate the diving time, which is visible in darkness.” While that sounds simple enough, the complete standard is incredibly long and detailed, covering everything from pressure testing to shock resistance to legibility in the dark to corrosion and magnetic field resistance.

(Photo Credit: W.O.E./James Rupley)

Many dive watches from brands like Seiko and Citizen closely conform to this standard but many others—from the luxury tier especially—do not, and here I’m talking about many of the original gangsters including the Rolex Submariner and Omega Seamaster and more modern legends like the Tudor Pelagos FXD. With that in mind, we should never limit our search for the perfect dive timer to timepieces claiming certification or compliance with the ISO standard.

Helium Escape Valves

(Photo Credit: Hodinkee)

One of the most misunderstood watch functions of all time, the concept of the helium escape valve is often thrown around in the professional dive watch conversation. In the briefest terms, a helium escape (or release) valve allows expanding helium atoms that have—because they are super tiny—sneaked past the gaskets in a watch case over the course of an extended period spent living in a dry, helium-rich saturation diving chamber to safely escape during the days-long decompression process without making the watch explode.

Unlike many dive watch features, the helium escape valve does its thing in the dry. (Photo Credit: Gavan Hennigan)

There are automatic valves like you find with the Rolex Sea-Dweller and manual valves like in the Omega Seamaster Diver 300. Both work more or less like a burp. As internal pressure within the watch case increases while external pressure, in the decompressing saturation system, decreases, the valve actuates, allowing the watch to equalize with its surroundings. If you are a commercial saturation diver who needs this functionality, you are most likely already aware. The rest of you do not and will not ever need such a valve no matter how extreme your scuba diving adventures at Sandals resort may become.

Final Thoughts

There are, of course, other aspects of dive watches that are important including a generally stout and durable build and a robust movement that can handle the knocks and bangs associated with diving and dive boats. That said, for this Dispatch, we decided to concentrate on the traits that are more specific to watches produced for the undersea environment. To summarize, we’re talking about appropriate water resistance, a method of measuring elapsed time, legibility in all conditions, and a strap or bracelet that will keep your dive watch right where it belongs. You don’t need one, but we also highlighted the helium escape valve’s incredibly rare but important work.

If dive watches can survive a wide range of underwater hazards, chances are they can take on your daily life. (Photo Credit: Brock Stevens)

Whether you intend to go diving or not, it’s important to understand the reasoning behind the basic dive design format that has become one of the most recognizable and popular watch silhouettes in horological history. Scuba diving remains relatively unpopular, but dive watches have transcended their intended use case and category to become the most popular overall sports watch type in part because of the capabilities they developed over decades on the wrists of military, professional, and recreational divers. And hey, even if you’re not going diving anytime soon, the bezel is great for timing whatever you have on the Big Green Egg in the backyard. 

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