What’s Water Resistance About?


It says "100m W.R." on your watch dial. And perhaps "10 ATM" on the watch’s caseback. You already know it refers to the watch’s maximum water resistance but is there more to it than those mere numbers?

If you have a 100m rated watch, would you wear it for scuba diving?

Well, why shouldn’t you? After all, the manufacturer labeled your watch as "100m water resist" and and you’re not likely to venture any deeper than 50 meters into the briny blue, so why not?

Perhaps your watch "looks like the very ones that you see professional divers wear on the National Geographic or Discovery Channel so you start thinking you could take your watch on your next diving trip too!

Then, you consult your watch owner’s manual and you get a shock. You learn that the manual states that your 100m rated watch is good for hand washing, showering and pool swimming only.

Sounds confusing? Why is a 100m rated watch good only for swimming and snorkeling only? What does the water resistance rating actually mean? Heck, I was once just as confused too! 🙂


The Basics of Water Resistance

Firstly, we need to understand that a manufacturer’s water resistance ratings for general watches are usually based on sterile, laboratory testing. They don’t really use real world conditions to test their products.


Generally, the resistance resistance properties of a watch is based on the following criteria:

  • The construction of the watch case
  • Design and condition of the rubber "O-ring" seals and gaskets
  • Thickness and hardness of the watch glass or crystal
  • Crown and push button design


Construction of the watch case

Generally, thicker cased watches are often employed for timepieces that are rated to 100m W.R. (Water Resistance) and above. The thicker the case, the stronger it can withstand crushing pressures in the deep. Some professional dive watches that have a rating of 600m usually made from titanium as it is lighter and stronger than stainless steel.

In the same vein, dress watches are not meant to be immersed in water, let alone worn for recreational or scuba diving. Dress watches are generally slim and their water resistance is usually limited to 50 meters or less. Although the manufacturer may state 50m W.R. rating, it doesn’t mean that you can take the watch to 50 meters in the water. At best, you can wear your watch in a swimming pool and that’s just about it.

At the other end of the spectrum, professional dive watches are often bulky and bulbous in design. Some have shrouds (like the Prospex SBBN011  1000m) to help fortify the watch case and also protects the case against accidental knocks and scrapes.



s_1000m (Medium) SSBS018J_1000m SBBN011_1000m (Medium)

Seiko’s three famous 1000m shrouded Professional divers in chronological order of production: the discontinued S23517J, SSBB018 and the currently sold SBBN011 “Darth Tuna"

Other professional dive watches have taken a different approach. For instance,  Sinn Hydro UX diver has a slimmer case than any of Seiko’s Professional 1000m divers.

Instead of increasing the thickness of the watch case, the Sinn UX is a silicone oil-filled watch to reinforce the watch’s structural integrity. Oil is virtually impossible to compress and strengthens the watch against extreme water pressure. In addition, the clear silicone oil filled dial assists in reading the time due to water refraction and reflection.

UXStrap UXGSG9Strap

Above: The oil-filled quartz Sinn Hydro UX (left) and the UX GSG-9 military issue model from its 2007 lineup

Since automatic movements can’t function in a viscous medium such as oil, Sinn used a high torque quartz movement instead. Silicone oil is an inert substance, it’s non-conducting and non-corrosive. You can see from the top right photo that the dial is quite readable from extremely flat angles.

The catch is that since the UX is a quartz watch, its battery will inevitably need to be replaced. As far as I know, owners will have to send the watch Sinn’s factory in Germany as the silicone oil has to be drained out before replacing the battery. The oil is then refilled and checked prior to shipping it back to the owner. That’s probably the most expensive battery change job I’ve ever heard in my life! 😉

Design and condition of the rubber O-ring seals and gaskets

All water resistant watches have rubber seals (whether natural rubber or synthetic) to keep out dust, moisture and of course, water. Higher W.R. watches tend to have thicker and more robust caseback gaskets made of higher quality rubber. Unfortunately these rubber seals don’t have an infinite life span. Rubber eventually hardens over time and will eventually develop cracks which will compromise your watch’s resistance to water.

If you have a diver’s watch that’s over 10 years old, it’s usually recommended to have all the gaskets and seals completely replaced. Like alternator and air-condition belts in automobile engines, rubber will eventually deteriorate and lose their sealing properties.

Although Seiko advocates annual checking or replacement of its watch seals, I personally don’t think it’s necessary unless you swim with your watch on a frequent basis. If you have a quartz watch, it may be a good idea to replace the gaskets on your next battery change, assuming the watch’s battery can run for 5 years or longer. For mechanical watches, you might want to have the seals changed when you take your watch for a periodical service – maybe once in six years.

Chemicals like chlorine, soap and detergents (e.g. taking a shower with your watch on) also help to hasten deterioration of  the rubber material. Therefore if your watch always accompanies you into the swimming pool, you might want to have the seals checked by your watchmaker or authorized repair center annually.

Thickness and hardness of the watch glass or crystal

Timepieces that are designed for scuba diving have thicker crystals to withstand water pressure compared to dress watches. The choice of crystal material, whether its made of mineral glass (Seiko calls their glass Hardlex), Sapphlex (Hardlex glass with a top sapphire laminate) and true sapphire crystals doesn’t influence a watch’s resistance to water pressure. Its thickness however, does.

Watches that are traditionally equipped with acrylic crystals, like some vintage watches such as the Seiko 4006/4005 Bell-Matic and the original Omega Speedmaster are not meant to be taken to swimming excursions, let alone taken along for diving.

Although Seiko’s first true dive watch – the 6217 or "62MAS" was also equipped with an acrylic crystal, the crystal itself had to be extra thick to withstand 150 feet of water pressure.

Acrylic crystals may not be as reliable as glass under pressure. In fact, Seiko’s second generation diver – the 6105-8000 model marked the manufacturer’s move from acrylic to mineral glass. From then on, all Seiko dive watches have crystals that are made from mineral glass or sapphire.


6217diver (Medium) 6105-8000-04 (Medium)

Seiko’s first diver, the acrylic crystal-equipped 6217-8001 (left) and its successor, the 6105-8000 (right)

Crown and push button design

All diver’s watches have screw-in crowns and seals for water-tightness. As long as the crown is screwed into the case snugly, the watch is water resistant to its indicated depth. Some sports watches also have screw-in crowns but they are not intended for scuba diving.

Very few diver’s watches have buttons or pushers that are designed to be operated underwater. These are usually models that have depth gauge sensors like the wrist dive computers that modern day divers wear. Seiko’s digital NX-series and its analog SLD005J have buttons that can be pressed underwater. Citizen also produces several Promaster Aqualand divers with depth gauges that can be operated while submerged. The buttons are specially constructed with seals that keep the water out when pushed in.

Such dive watches are usually costly and those who buy such timepieces are usually people (like certified PADI dive instructors) who actually go scuba diving on a regular basis.


SBDK001J SLD005P JV0020-04E (Medium)

Specialized dive watches such as the above allow underwater button operations. From left to right: Seiko NX-series, SBDK001, SLD005J and the Citizen 20th Anniversary Aqualand JV0020-04E.

Seiko also makes ISO-certified diving watches with buttons, such as the SBDQ001/003 and SNDA13/15P chronographs and several Kinetic divers with power reserve indicator buttons (the 5M-caliber series). These buttons are however, not designed to be operated when submerged. Doing so will allow some water into the case and perhaps flood the watch, damaging the movement.

For this reason, Seiko’s owner manual explicitly states "Do not operate the buttons when the watch is wet for their non-professional diver’s watches.

SBDQ003 (Small) SNDA15P1 (Medium) SKA367P1_4 (Medium)

These ISO-certified Seiko divers should not have their buttons depressed while underwater: the SBDQ003 and SNDA13P quartz chronograph  divers and the yellow SKA376P Kinetic diver.


How watches are tested for water resistance

Watch manufacturers’ water resistance ratings are based on sterile laboratory testing. Generally non-diver’s watches are subjected to static dry pressure tests, which involves placing watches into a dry pressure chamber. Pressurized air is then pumped into the chamber up to the intended pressure to simulate depth in water.

Should the watch have a leak, the case will slightly expand which means that the watch allowed some air into the case, hence failing the pressure test. Either the rubber seals didn’t hold up to the pressure or the watch glass wasn’t fitted properly.



Above: A wet chamber pressure tester. Photo courtesy of Kineticrepair.com

The manufacturer can also use the wet pressure testing method, which involves pumping pressurized air into the watch in a chamber. The watch is then immersed in water. If there’s a leak, bubbles will escape from the watch. failing the water resistance test.

The timepiece is then inspected and rectified or even discarded as a defective unit, depending on the manufacturer’s quality control policy.


Here’s an excerpt from Wikipedia, relating how standard watches are tested for water resistance:

ISO 2281 water resistance testing of a watch consists of:

  • Immersion of the watch in 10 cm of water for 1 hour.
  • Immersion of the watch in 10 cm of water with a force of 5 N perpendicular to the crown and pusher buttons (if any) for 10 minutes.
  • Immersion of the watch in 10 cm of water at the following temperatures for 5 minutes each, 40°C, 20°C and 40°C again, with the transition between temperatures not to exceed 5 minutes. No evidence of water intrusion or condensation is allowed.
  • Immersion of the watch in a suitable pressure vessel and subjecting it to the rated pressure for 1 hour. No evidence of water intrusion or condensation is allowed.
  • Exposing the watch to an overpressure of 2 bar, no more than 50µg/min of air is allowed to get inside the case.
  • No magnetic or shock resistance properties are required.
  • No negative pressure test is required.
  • No strap attachment test is required.
  • No corrosion test is required.

In practice, the survivability of the watch will depend not only on the water depth, but also on the age of the sealing material, past damage, temperature, and additional mechanical stresses.

None of the tests defined by ISO 2281 are suitable to qualify a watch for scuba diving. Such watches are designed for everyday life and must be water resistant during exercises such as swimming. They can be worn in different temperature and pressure conditions but are under no circumstances designed for diving with underwater breathing apparatus.



The water resistance table

Let’s take this water resistance chart that Seiko prints on its website and learn to interpret what the chart describes.



Seiko’s Water Resistance Chart

As you can see from the chart above, it states that if the marking on the case says "5 BAR" (translation: 1 Bar = 10 meters, so 5 Bar = 50 meters) the watch could only be taken for "swimming, yachting and taking a shower". So how come bathing and shallow diving is not permissible? Your bathtub is surely no more than 1.5 meters deep. And your average swimming pool couldn’t even be twenty meters deep, could it? 😉

Watch manufacturers usually furnish water resistance capabilities conservatively. They base their recommendations on the fact that you’d want your watch to last as long as possible. Compare the 20 Bar entry against the Diver’s watch 200 meters. According to the table, 20 Bar rated watches are good up to "bathing and shallow diving" while the Diver’s watch is permissible for scuba diving.



Can a 50 meter W.R. watch taken down to 50 meters underwater?

Theoretically, you can. If the rubber seals are fairly new, your watch has a good chance of surviving to 50 meters in water. But then we have to remember that non-diver’s watches are tested in lab conditions using static pressures, which do not exist in real world situations.

In the depths of a body of water, undercurrents exist. The act of swimming against water and currents also create dynamic pressure, which is exerted upon the watch that you’re wearing. Therefore  at just thirty meters beneath the ocean, the water pressure that you and your watch can be a lot more than 5 Bars, which goes past the manufacturer’s water resistance rating.

Even a simple act like jumping off a high diving board into a swimming pool can result in a pressure which exceeds the watch’s design limitations. You may end up with a deformed watch case or a cracked crystal due to the impact. Which can lead to water intrusion and damage to your timepiece.

A rough-but-simple analogy would be comparing a sports car with an economical sedan for daily commuting. It’s fairly easy for a normally aspirated 1.5 liter Honda Civic to be driven at 180 kilometers an hour on a long, flat road. Sure, if you’re the only one in the car with no luggage load and given the right conditions like no headwind and a with the assistance of a slight downhill gradient, you might be able to hit even 200 km/h. 😉

However, if you drive the Civic like this too often you’re actually exceeding the car’s intended design – and at 200 km/h your engine revs would be hovering on the tachometer’s redline. Keep this up frequently, sooner or later your engine will wear out quickly. It’s just that the Civic’s small engine wasn’t designed to be driven frequently at that speed in the first place.

In contrast, a Chevrolet Corvette sports car with a big engine block could easily attain the same speed without even breaking a sweat. Its huge engine power and torque enables it to cruise at 200 km/h effortlessly with the engine ticking over at a leisurely pace. Obviously the Corvette was designed for reliable, sustained high speed driving whereas the 1.5 liter Civic was not.



Corvette (Small) civic

The two famous "C"s – the Corvette and the Civic. One was made for pure speed, the other for fuel economy (illustration purposes only)


Similarly, you could take your 50-meter W.R. rated watch to fifty meters underwater but if you do it too frequently, you’re risking your watch’s water resistant integrity. You’ll be stretching your watch’s water resistance limits to the max.  For this reason watch companies make watches that are specifically designed for recreational and deep sea diving.



Is a 200m sports watch the same as a 200m diver’s watch?

The short answer is NO. Although both watches are rated to 200 meters. there is a not-so-obvious difference between the two.

Although both watches have the same water resistance rating, a diver’s watch is constructed to withstand water pressure reliably at the indicated depth plus some 10-15% overhead for an extra measure of safety and reliability. Unlike an ordinary 200m sports watch, a  200m diver’s watch is designed to be survive high stresses in the long term.

Additionally, a diver’s watch also has to meet several criteria before it could be certified as a diver’s watch. When watch manufacturers design a diver’s watch, they have to meet the International Standards Organization (ISO 6426) requirements.

The criteria for an ISO 6426 diver’s watch include the following:

  • A minimum of 100m (330ft) depth rating
  • A watch case with the ability to resist corrosion from sea water, dust, shock and magnetism
  • An easy-to-read, legible dial with distinguishing hour markers for 12, 3, 6 and 9 o’clock
  • Differently shaped luminous hour, minute and second hands
  • A luminous dial for reading the time in darkness
  • An elapsed time recorder such as a timer, stopwatch or unidirectional rotating bezel
  • A water-resistant, screw-in crown
  • An end of life (EOL) battery indicator for quartz watches (second hand ticks erratically to indicate the need to replace the cell). Mechanical divers need to be sufficiently wound before diving while Seiko’s Kinetic divers have a push button or a real-time power reserve gauge to indicate the reserve of their internal storage cell.

         7549-7010 (Medium)  lume_mission_antarctica

        Although the Citizen Mission Antarctica (right) has bright luminous dial and hands, it does not qualify as a true diver’s watch like the vintage Seiko 7549-7010 Professional 300m (left).

      You may have noticed that all true diver’s watches have a lumed "ball" either at the tip or at the opposite end of the second hand. The placement of the lumed ball doesn’t really matter as the primary function of the second hand is to let the wearer know that the watch hasn’t stopped working underwater.

      Recreational and professional divers don’t really need precise timing up to the nearest second. For this reason, most analog quartz divers’s watches have no need for a stopwatch. The rotating bezel on these watches is sufficient to indicate the elapsed diving time up to the nearest minute.

      A 200m sports watch may look like a real diver’s watch but it does not comply with the ISO 6426 standard requirements.Therefore, there is the element of risk if you wear a 200m sports watch instead of a true diver’s watch for long term diving activities.



      Although both Seiko Atlas models are rated to 200m with screw-in crowns, neither are true diver’s watches.


      Actually, there’s nothing really wrong wearing a sports watch for scuba diving. Some people have claimed to have no problems wearing their 100m W.R. watches for shallow scuba diving but they’re actually risking their timepieces in the long term. If you’re lucky, your non-diver’s watch can last for years without damage. In other words, your mileage may vary.

      Watch companies make  diver’s models for a reason – it’s not just to make profit but to ensure that they offer reliable timepieces that are designed specifically for the job.



      What happens when water enters your watch?

      In the case of a flooded mechanical watch, the damage to the movement can be contained if the watch is taken for repair as quickly as possible before rust sets in.

      Since an automatic watch movement is largely made of plastic, brass and steel parts, the parts can be disassembled, rinsed carefully, dried, re-oiled and re-assembled. However, if the dial and hands have also gotten wet, they need to be replaced.

      With non-mechanical timepieces, including quartz, Kinetic, Spring Drive and solar powered movements, the damage is usually irreversible. This is because microelectronic components constitute part of the internal movement and the components are likely to have shorted out beyond repair.

      Most quartz modules use surface mounted semiconductors like any other electronic device. The only recourse is a complete movement/module replacement – assuming the watch parts are still available from the manufacturer. If it’s a vintage quartz model, you’re out of luck. 🙁



      Watches that you should never take for a swim

      As a general rule, any watch that do not have "water resistant" markings or with no indication of the W.R. depth should never be worn for a swim. Usually thin dress watches aren’t water resistant unless the manufacturer states the degree of water resistance.

      Then again, if your watch originally came with a leather strap you definitely won’t want to expose it to water. 😉


      Here’s my personal list of watches that you shouldn’t risk taking into the water:

      • Any Seiko watch that does not say "water resistant" on the dial or the caseback.
      • Any Seiko watch that has the "water resistant" text but no indication of its depth rating. These are good up to 30 meters but Seiko only indicates the depth rating for their 50m models and higher.
      • Rare, vintage watches that you really care about.
      • Any diver’s watch with gaskets and seals that have not been replaced for several years and has not undergone a recent pressure test.
      • Early Tissot T-Touch multifunction watches (except the new T-Touch Expert)



      SNX115K 6139-6002 (Medium)

      Better keep these on dry land: A basic Seiko 5 (30m) and a vintage 6139-6000 chronograph (70m)


      Umm, I thought it was worth mentioning the Tissot T-Touch. 🙂

      The Tissot T-Touch used to be a watch that I lusted after sometime ago, when it first came out. It’s a shame that for a multi-function watch with a digital compass, altimeter, barometer and thermometer, Tissot rated it only to 30 meters. A fine watch for hiking and mountain climbing, but taking it swimming is a no-no.

      According to my watchmaker, the T-Touch has a tactile touch screen that’s too sensitive to be pressed strongly by the wearer’s finger (you’re supposed to touch the crystal gently, not jab on it!). I guess that made some sense as swimming in a pool will exert enough pressure on the crystal, possibly damaging the delicate sensors.

      Recently Tissot has introduced new 100m W.R. T-Touch models, named the T-Touch Expert. Apart from the vastly improved water resistance rating, the Expert also includes a sorely needed backlight for the LCD display.


      T33.7.488.61 T33148871a

      The first generation T-Touch with the green "T" logo and the 2nd generation with the red "T". With a measly 30m water resistance, neither watches are suitable timepieces for swimming.



      Whether you want to take a non-diver’s watch for scuba diving or a watch with a low water resistant rating for swimming activities is entirely up to you.

      I learned this the hard way when I immersed my old Seiko H557 analog digital watch (it indicated "water resistant" on the caseback) into a bucket of soapy water to get rid of the built-up gunk and to pry off the Seiko quality control sticker that had stuck on the caseback since 1984. Sure, it got the watch spick-and-span and the sticker did come off.

      It wasn’t until the next day I had the battery replaced, my watchmaker pointed out to me that some water had gotten into the watch. It turned out that the damage was very minimal and the watch functioned perfectly. What a relief!

      In 1998 I purchased my first Seiko analog watch – a 7T32 caliber SDWD19P and took it for a dip in a hotel’s swimming pool. It has a 50 meter W.R. rating and I thought, "what the heck, the pool is hardly 2 meters deep anyway" so I swam with it. I remembered timing my swim and pushed the buttons when it was wet.

      Fortunately for me I had the presence of mind not to operate chronograph buttons while submerged and the watch is fine right till this day. 🙂

      Img_0344_resize (Small) sdwd19p_0194_resize (Small)

      Two of my old Seikos that survived water intrusion by sheer luck: the H557 analog digital (left) and the SDWD19P (right)


      From then on I make it a point to wear at least a 100m rated watch to the swimming pool or better still, my SKX007J diver. 😉




      Did you enjoy this post? Why not leave a comment below and continue the conversation, or subscribe to my feed and get articles like this delivered automatically to your feed reader.


      Interesting article. well done.
      The ISO description for dive watches seem to cover legibility on analogue styled watches, i wonder what the criteria is for digital.
      What i don’t get about the Seiko Kinetic diver is why didn’t they have a screw down security lock for the power reserve button, which i’m sure would get bumped underwater sooner or later.=p


      Thanks Julian.

      I’m sure the ISO standards also apply to true digital diver’s watches. As long as the LCD display is very legible and equipped with a backlight it should qualify as an ISO rated diver’s watch.

      The Seiko NX digital divers are essentially dive computers and they are quite expensive. All dive computers are digital based and their buttons should be operable underwater.

      The 5M-series Kinetic divers have small and recessed PR buttons and they’re unlikely to be accidentally pushed in any case, unless the wearer absent-mindedly presses it. 🙂


      =] i was looking at the picture you put up
      SKA376P it just looks so “press me”
      yeah i guess its unless you really mean to press it
      the button would sit untouched.


      Hi Quartzimodo,

      I can tell you the T-Touch is not suitable even for climbing/riding. The T-Touch I had on failed after rain soaked through my riding jacket on the N-S highway. Guess what the technician told me after I had it repaired under warranty?

      Don’t let it touch water.

      Some sports watch eh?

      Nice to see one of my fav. blogs back online. Gave you a scare huh? Did you manage to update your WordPress?

      Hi Vandice,

      I nearly bought a T-Touch back in 2003 and it was about RM1.5K after discount. Fortunately my watchmaker advised me against it (although he sells Tissots).

      I researched on the ‘Net and found a few negative reviews from local owners. And the 30 ATM W.R. rating is a joke. I feel much safer with my Casio ProTrek PRG110 Triple Sensor watch. 🙂

      With the budget for the T-Touch I got my myself the rare Seiko Sky Professional and couldn’t have made a better choice.

      I’ve met quite a few people in public wearing a T-Touch but have yet to meet anyone with a Sky Pro on their wrist. 🙂

      Oh yeah, I managed to restore my WP files manually – I don’t want to upgrade to ver 2.6 yet as some of my plugins aren’t updated for the latest version.

      Thanks for voting my blog as one of your favorite ones, really appreciate it. 🙂


      Ironically, I just bought Tissot T-Touch Polished Titanium (T33.7.888.92 or Z253/353P) :). I stumbled with LOTS of complaints/issues/problems about it, but, my friend, who bought stainless steel version recently, told me that Tissot has improved it’s quality, which also similar with the message which I got from Tissot reps today :). I send them my watch’s serial number, and confirmed it is the latest version/badge of T-Touch. I hope my new watch is as longlasting as my other 2 Seikos. 🙂

      One thing for sure, Titanium version is very light, 33% lighter than stainless steel version (150 g vs 100 g). Polished titanium gives a very distinctive shining, which is not like ‘usual Titanium’ color, but more toward to silver, and even shinier than my 10 year’s old silver engagement ring :).

      This is what it’s look like. (Sorry, the site is in Japanese, but the pictures are very good)


      The carbon fiber dial looks very sporty and cool.

      BTW, I am just a person, who sit and working in front of computer more than 8 hours a day, and the probablity of my T-Touch ‘touches’ water is almost 0 percent.

      Okay, I may continue this soon… 🙂

      Anyway, Seiko is still my favorite. I am interested in Seiko Spring Drive watches, but it is VERY expensive right now. Seiko Thermic also nice, hope I can see/touch it in future.

      Thank You.

      Hi Baha,

      Congrats on your purchase of the T-Touch. People who own dive watches but don’t get their watches wet are often called “desk divers”. 🙂

      I certainly hope your new T-Touch is more resilient than the early versions (the ones with the green “T” logo). It’s just that I find it ironic that Tissot touts the T-Touch as an outdoor watch but a mere 3 ATM (30m) water resistance rating means it’s just as water resistant as many basic Seiko 5s.

      For outdoor use, I’d rather wear my Casio Protrek PRG110V Triple Sensor. 🙂

      Seiko and Citizen both have polished titanium models, especially in their upper end Brightz and Promaster ranges respectively.

      Spring Drives are very expensive and Seiko Japan has very few technicians trained with these new technology movements. Currently only Seiko Japan can service SD watches.

      As for the Seiko Thermic, it was an experimental technology that didn’t work that well in real life (it depended on the thermal difference between your skin and the atmospheric temp) and Seiko dropped the idea. Seiko Thermics are mostly in the hands of serious watch collectors today and I doubt they are worn as every day wrist wear. 🙂


      […] Firstly, I’d like to state that the SHF-series Kinetics and its successors are not ISO certified divers’ watches. They are merely water resistant sports watches that resemble diver’s watches. For an in-depth explanation on water resistance, you may want to read my previous blog entry. […]

      onde posso encontrar esses modelos para poder comprar

      Você tem que ser mais específico com a sua pergunta, Auteny. Que vê o senhor está se referindo?


      Oi, acabei de comprar um Seiko Monster Oranger e gostaria de saber se alguem já mergulhou com um desse ou se tem algum relato sobre isso! gostaria também de saber quantos metros de profundidade real, não em testes de laboratório, esse relógio aguenta, pois ele tem escrito scuba diver’s 200M
      Sepuderem me mandar resposta ficarei muito grato!!!!
      Desde já muito obrigado pelo espaço!!!! ABRAÇOS

      Hello great blog. Im a technical diver and this was very interesting to read. Nice to see some heavy dive watches being discused. I own two pictured watches in this article…the Seiko NX and the Citizen Pro Master like the ones you have up top on this page. The NX is a true air/nitrox dive computer and is infact manufactored to 1000m resistance and the other is the Citizen ProMaster to 200m but its only a depth gauge with accent/time warning. For some reason I use the promaster alot more than the Seiko because it seems far more durable and never need to worry about batterys with the EcoDrive solar. The interesting thing about the Seiko NX is that Seiko built the watch case to withstand 1000m and I read somewhere the depth sensor will read to 200m before folding but it was de-rated to 99.9m for legal reasons. I read somewhere they were worried if the unit was used as a sole diving computer and a tragety happened. I will say the NX is a very basic unit as many important features like other computers have are missing. Seiko always had lovely buttons with sleeves and soft smooth pressure. I found the Citizen to be clicky and somewhat wobbly in the button tubes. As far as pressing buttons under water….I would just not do that. Even if the manufactor says its ok. Set everything before decending and just leave it be. I have a IWC 2000m that leaked water through the second crown. Lucky it was under warrenty and had it sorted out free. Also with the ISOs there are several standards that a true dive watch needs to meet. ISO 6425 and also ISO 2281, ISO 2859-2, ISO 2859-3. The second lot of testings dose not classify to dive standards but is part of the whole test procedure that the dive watch needs to meet.
      Once again fantastic reading.

      Hi Thomas,

      It’s great to hear the inputs from a professional diver! Being expensive dive computers, the Seiko NX is out of reach from most Seiko collectors and those who collect them, tended to go for the entry level 200m NX models. However, there’s no shortage of 1000m diver’s watch fanciers but they prefer analog versions such as the SBBN011 “Darth Tuna”, SSBS018 and S2351J (all quartz). These shrouded hockey puck-like watches are all business and very tool-like looking. They’re made to perform in harsh conditions rather than being mere “drawer queens”.

      I sometimes wonder if Seiko had ever considered oil filled watches like the Sinn UX. They could have made such a watch if they wanted to but perhaps decided that ease of battery replacement and maintenance takes precedence.

      Thank you once more for your comments and the additional information on the other ISO standards that you’ve posted, which I’m sure other readers would find useful. 🙂


      Seiko does make Kinetics that are diver’s type watches with screw-down crowns. If your watch does not have a screw-down crown, and if you do not have the seals replaced every couple of years (all the seals – crown, caseback and crystal gasket, and/or push button gaskets) then do NOT assume the watch is water resistant. Another fact of information is that any watch that is a true “diver’s rated” model will have been individually tested for its rated water resistance at the factory. A model that is not rated as a professional diver’s watch will not have been individually tested – rather the case-type is tested and verified. The various ISO standards are interesting in this regard.

      Hi John,

      Thanks very much for the valuable insights to the subject matter. I did wonder if ISO rated dive watches are individually tested prior to passing the QC check, but as I couldn’t verify this I decided not to write this into the post. You are correct in saying that Seiko makes Kinetic divers – they all come with screw-down crowns. Such models include the modern SKA36xP “Big Freakin’ Kinetic” and the SKA289P/291P/293P “Big Boss” models.

      Seiko also made various professional-grade ISO divers like the 5M45 caliber Scubamasters with a GMT hand in the past. They’re both scarce and expensive watches and often a favorite trophy watch for die hard Seiko diver’s watch collectors.



      Hello Quartzimodo,

      Another highly technical & well done article Sir, and you have my congratulations for touching on just about all phases of Water Resistance, and I learned a few things I didn’t know by this one.

      As always, I was glad to find this article by you and your blog is one of the Best Top resources available for the technical watch collector or trained Diver interested in obtaining unbiased facts of finer Horology related seafood cusine!

      Cheers Stratman & well done with many thanks,

      Hi Jimmy,

      Thank you for the comments. I did this post years ago that I can’t remember how I wrote it but suffice to say I spent days refining my knowledge on the subject. Many people have no real clue as to how water resistant their watches are and often than not, the general assumption that a 50m W.R. watch is suitable for scuba diving as they “don’t dive that deep”. Hopefully my article sets the record straight once and for all. 🙂


      Just came across you site and was amazed at your ability and knowledge on these vintage Seiko watches. I looking to replace my divers watch that I used in the Mekong Delta, while diving in the brown water navy to ensure our troop were safe in the USNS that were used to house transient marines and army personnel until completed training and moving on to their units. Anyway, I had a great watch which I see occasionally/often see on ebay. The watch that I used was a 6139 000 and the serial Number was dated I believed in The early months of 1971. Brought the watch back to the states in 72 and put it away. I gave it to one of my nephews for graduation in 88 and I never saw the watch again. I’ve asked him what he did with it and doesn’t have a clue. In fact I don’t think he even remembers me giving it to him. I see them on ebay occasionally, but I’ve noticed the saphire cyrstals have been replaced. I was wondering if you sell early 69-70 6139 in decent shape.
      Kindest Regards,
      Gale S. Lofstrom, USN Ret. SD

      Hi Gale Lofstrom,

      Than you for sharing your experience with your vintage Seiko 6139 automatic chronograph with us. The caseback digits are however incomplete; if you meant the 6139-6000 then it’s one of the very popular and well-loved 6139 chronographs. Seiko made quite a few variants based on the 6139 caliber and I own two of these myself, a 6139-6002 and a 6139-7010, if memory serves me well.

      However I find it unusual for US servicemen in the field during the Vietnam wearing something like a 6139 chronograph as its luminous hands and markers aren’t as bright as a Seiko diver’s watch like the 6105-8000 or the 6105-8110, which also have better water resistance properties.

      If you’ve watched the epic Vietnam War film “Apocalypse Now” from 1979, you can see the character Capt Benjamin Willard (Martin Sheen) wearing a Seiko 6105-8110 diver during the PB gunboat scenes as he goes through the dossier papers.

      But then that’s fiction. I’d guess in real life, US servicemen had access to various Seiko models at the PX. 🙂


      good job man.. seikos are g. ive got a skx007 this site helped cos i got a cheap casio gshock water resist 20 bar

      Talking about Seiko 6139-6002 chronograph. I am in the process of getting this watch, a 1972 model which I acquired second hand back in 1975, restored. Problem is I cannot get hold of the crystal gasket – any thoughts, suggestions, contacts would be greatly appreciated.

      Hi Brian,

      I have the exact 6139-6002 as you do as it’s a popular 6139 model amongst vintage Seiko collectors. Although I don’t have anything done on it, I once purchased a genuine Seiko crystal for my 6138-0030 chronograph from Jonathan Koch, also known as Mr Seiko on eBay. He’s based in New York, if my memory serves me well.
      Jonathan is the only person I know who sells NOS parts for Seiko watches on eBay and he would know if the 6139-600x crystal gasket can be substituted with one for a different model. There are some circumstances in which the same part can be shared amongst differing Seiko models.

      Best of luck in your hunt! 🙂


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