A MythBusting Guide To Water Resistance

Tired of being confused about how water resistance works with watches? Tired of diving down the rabbit hole to find answers, only to receive contradictory information? Look no further, this MythBusting guide is for YOU!

I have compiled a list of some of the most common myths about water resistance, which I will attempt to debunk here. My knowledge comes from empirical experience of being a watch collector - specifically dive watches - for over 10 years, plus a wealth of research I have found from some very smart people on the internet, which I will provide sources for. I will also provide some personal opinions, which will be clearly marked as such. I will try not to speak in absolutes, because there are exceptions that I might miss.

For ease of navigation and quick referencing, below you will find a list of the 8 myths/topics covered in this post, in order of appearance. You will still have to manually scroll to get to each, but hopefully this gives you some sense of how far down the page to go.

• Topic #1: Limits Of Waterproofness [Myth Discussed: It Is Possible For A Watch To Be 100% Waterproof]

• Topic #2: Screw Down Crowns [Myth Discussed: A Screw Down Crown Directly Provides Water Resistance]

• Topic #3: Push-Pull Crowns [Myth Discussed: A Push-Pull Crown Is Not Sufficient For Water Activities]

• Topic #4: Depth Ratings And ISO Standards [Myth Discussed: The Stated Water Resistance (M/Bars/ATM) Means The Watch Can Always Go To That Depth Without Being Compromised]

• Topic #5: Alternative Standards To ISO [Myth Discussed: ISO Is The End All, Be All Of Water Resistance Standards]

• Topic #6: Dynamic Pressure [Myth Discussed: Dynamic Pressure (Movement) Adds Significant Amounts Of Pressure On Top Of The Static Pressure Already Being Experienced]

• Topic #7: Using Watches In Hot Environments [Myth Discussed: Watches Can Never Be Used In Hot Environments Such As The Shower, Hot Tub. Etc.]

• Topic #8: Water Resistance For Vintage Watches [Myth Discussed: I Can Take My Vintage Watch Into The Water]

Okay, let's dive in! (oh geez, he's already doing puns...this is going to be a long one).

MYTH #1: It Is Possible For A Watch To Be 100% Waterproof

Commentary: We'll start with the easiest myth to bust first. There is no watch that is 100% waterproof under all circumstances.

There are plenty of watches designed to go in the water, and if used in accordance with the manufacturer's specifications, will keep water out assuming all parts are in working order. But there's always at least a small margin for failure due to many factors. I won't spill any more virtual ink on this one, but here is a great article from Hodinkee on the topic which explains why the term "waterproof" fell out of favor by the mid-20th century. https://www.hodinkee.com/articles/why-no-watch-is-waterproof

MYTH #2: A Screw Down Crown Directly Provides Water Resistance

Commentary: A screw down crown is an essential feature of any dive watch worth its salt (my opinion), however the actual waterproofing is done via gaskets. Gaskets are placed around various parts of the watch susceptible to leaks, such as the crystal, bezel, case back, and crown. As an example, the case gasket sits between the case and case back. When the case back is attached to the case, it sandwiches the gasket causing it to compress and expand slightly. This expansion ensures the gasket makes contact with every part of the metal, creating a seal against water and dust. The other types of gaskets work in a similar way.

So let's talk specifically about crown gaskets. You will find a variety of crown gasket configurations depending on the brand, the purpose of the watch, and the price (some higher-end models may have more complex gasket systems). A pretty standard configuration is to have 1-2 gaskets placed somewhere on the crown stem. These gaskets expand inside the crown tube, creating the seal. Here's an example:

[Source:https://seikoparts.wordpress.com/2018/06/28/introducing-the-s-crown-a-sarb059-alternative/]

On some designs, the gasket is located inside the crown tube instead of on the stem - for instance, I believe some of the entry level Orient divers use this configuration. This isn't an Orient watch, but here's a picture of what that looks like:

[Source: https://www.watchuseek.com/threads/where-does-the-gasket-go-in-this-crown.4850635/]

Some more advanced designs, which might be found on "professional-grade" dive watches, may contain additional gaskets for added protection. The Rolex Triplock design is a good example of this:

As you can see, Rolex technically uses 5 gaskets (if we're counting the O-rings) in their crown design...talk about over-engineering awesomeness!

Something important to note: as I said, the screw down crown doesn't directly provide water resistance - HOWEVER - some designs, like Rolex, have additional gaskets that are engaged when the crown is in the screwed down position. These gaskets are often positioned on the outside of the crown tube, and/or inside the base of the crown (as you can see on the Triplock diagram). The seal is created only when the crown is screwed down. This is merely an added layer of protection, and the watch would still be water-resistant without it due to the gaskets that sit inside the crown tube.

This also means that technically, your watch will maintain water-resistance while submerged even with the crown pulled out because of the inner tube gaskets (don't try this at home!). That said, as soon as you start to move the crown while it's pulled out, the gaskets will move with it and very likely create gaps for water to get in. This is where we get to the heart of the matter as to why a screw down crown is really valuable. It ENSURES a crown cannot accidentally or purposefully be pulled out and manipulated while in or under water, preventing the time from being changed (if you're using your watch to time dives) and preventing water from accidentally getting inside.

A small sub-topic is diving chronographs. To my knowledge they use the same principles - the two pushers will also contain gaskets and often screw into the case just like the crown so they can't be operated underwater. Non screw down pushers in theory should maintain water resistance as long as they are not operated underwater (my opinion - still a risky proposition). EDIT: thank you to @Waybe_6 for pointing out in the comments that Fortis produces a dive chronograph(s) that allows for use of pushers underwater. I don't know how that technology works, but it sounds pretty cool. I suspect some other brands might have a similar solution for this, I just don't personally know much about dive chronographs.

Marc from Long Island Watch put together a 2-part video series about water resistance which explains all of this with some very helpful visuals. Here is the link to part #1 which mostly discusses the gasket systems: https://youtu.be/uQFuZL14Aaw?si=xdpXw2Kwx1txG1BL

MYTH #3: A Push-Pull Crown Is Not Sufficient For Water Activities

Commentary: Building off of myth #2, you might have heard that only watches with a screw down crown can be used in or around water. This is false!

Remember, water-resistance is achieved by gaskets, not by the crown itself. If a watch contains the proper gaskets and they are all in working order, then in theory, it should have at least some level of water resistance. That being said, as explained earlier, the screw down crown gives you protection from the crown accidentally or purposefully being pulled out and manipulated. Obviously, a push-pull crown does not have the same level of protection, which may matter to you or maybe not...just something to keep in mind. There is still a distinction though between watches that are specifically engineered for scuba diving versus those that provide just basic water resistance but are not certified for dive use.

My opinion: if a watch does not have a screw down crown, it might mean it was not specially designed to be used in or around water as its primary purpose, and therefore has not been tested to a robust standard for that type of use (more on testing later). This doesn't mean you can't use it in that manner, just that it may not have the ideal features for water resistance. This is merely my GENERAL rule of thumb, there are certainly exceptions. In any case, my best advice is to know the specs of your watch and its limits before taking it near water.

MYTH #4: The Stated Water Resistance (M/Bars/ATM) Means The Watch Can Always Go To That Depth Without Being Compromised

Commentary: Do you like the “always” I threw in there? That was the classic dead giveaway on the True/False test questions in school that the answer was going to be false.

For starters, a quick point of clarification. The depth rating on a watch refers to the atmospheric pressure experienced at that depth, not just the distance below the surface. Depth rating is most commonly expressed in Meters, Bars, or ATM (atmospheres).

So, whether a watch can be taken to its stated depth or not really comes down to one word for me: TESTING. What type of testing, if any, has the watch been put through by the manufacturer to certify the depth rating that is being marketed? That is the key question.

Testing is an expansive and complex topic when it comes to water resistance. I'll do my best to hit the main points but there is so much info out there. You might be familiar with the International Organization for Standardization (ISO), which has created two different standards for watches, one for basic water resistance such as incidental contact and basic water activities (ISO 22810) and one specifically for dive watches (ISO 6425). 6425 also contains a section on requirements specific to saturation diving (which I won't cover here, but good to know).

ISO is one of many standards that might be used to certify water resistance (I'll discuss other standards later). Importantly, ISO only creates the standards, they do not certify the watches themselves [source: https://www.iso.org/certification.html]. So if a brand says they meet ISO specs, that doesn't necessarily mean that claim has been verified, nor is it required to be. Any reputable brand, however, will (in theory) be responsible in how they market their watches and not make false claims about being ISO compliant.

Here is a forum post that explains the basic tests for each ISO standard. https://www.watchprosite.com/horological-meandering/here-s-the-iso-standard-for-water-resistance/17.1281476.10820301/

Alternatively, good ole Wikipedia also has the same info about the tests: https://en.wikipedia.org/wiki/Water_Resistant_mark

If you want to see the full standards, you can purchase the full documents from ISO or do additional research on your own if you're interested in the ISO standards, but I don't want to get too in the weeds here.

Here are the important takeaways for each standard. If ANY watch from ANY brand wants to make the claim that it is water resistant (and have the right to print the words water resistant/water resist somewhere on the watch), it MUST pass the ISO 22810 standards at its stated depth, whether that is 30M, 50M, 100M, etc. [source: https://www.iso.org/news/2010/11/Ref1367.html]. Here are examples of how that text might appear on a watch:

So that all sounds great, right? There's a catch. To meet ISO 22810, only a sample of the entire batch of watches has to meet the standard, and the manufacturer is free to choose their own sampling plan [source: https://www.iso.org/news/2010/11/Ref1367.html]. So what does this mean? In all likelihood, it means that the specific watch on your wrist which bears the words "water resistant" has not been physically tested for water resistance. In theory, you should be able to take the watch to its stated depth, but in practice, it might be a different story.

Keep in mind, these are minimum standards. It's quite possible some brands go above and beyond the 22810 standards with their testing, but don't quite hit 6425 standards.

If you're in doubt, remember the 2 Rs: RESEARCH AND REPUTATION.

If you're not sure what type of testing your watch has undergone, research it. If you're still not sure, if the watch has a historical REPUTATION for being used in and around water, you can generally trust that. The Orient Kamasu pictured above is a good example of this. This watch (as well as some of their other entry-level divers) does not meet ISO 6425, but it has a historical reputation of being successfully used in and around water, although it may not be the preferred choice for professional divers.

For ISO 6425, if any brand wants to certify its watch as an ISO Diver's watch, which gives them the right to label their watch with the word "Diver's" - it must pass the ISO 6425 standards, which are far more rigorous. Notably, EVERY SINGLE WATCH, not just a sample, must undergo the tests. The stated depth must also be tested at 125%, meaning that to rate a watch for 200M, it must have passed the pressure tests at 250M. As you can see, you have significantly more assurance that an ISO 6425-certified watch can actually perform at its stated depth and even beyond. Example of the Diver's text:

As a side note, to tie into the earlier discussion on crowns, ISO 6425 does not explicitly require a screw down crown. However, it does have a shock test which involves the crown receiving a perpendicular impact while at 125% of stated depth, wherein the watch must maintain water resistance after the impact. I would posit that many manufacturers have found that a screw down crown - in addition to the extra security it provides - is a simple, proven solution for passing this test, but I wouldn’t be surprised if there are alternative non-screw down designs that fulfill this requirement as well.

So what's the main point here? To reiterate what I said during Myth #3, know the specs of your watch and its limits before taking it near water. Don't just assume that the depth rating listed is gospel and means you're always good to go. Have an understanding of the type of testing, if any, the watch has undergone as well as its general reputation among the watch community.

My opinion: a Seiko Presage, for example, which might display the mark of 100M water resistance, was not built for water use as its primary purpose, even though in theory or in practice you could bring it in the water, and it’s your right to do so. Just bear in mind, when you use watches for purposes they weren’t specially designed for, their standards for design and testing may offer lesser assurance of water resistance. This is merely my GENERAL rule of thumb, there are certainly exceptions.

So then, if a watch doesn't have the words Water Resistant/Water Resist/Diver's, what does that mean? Onto the next myth!

MYTH #5: ISO Is The End All, Be All Of Water Resistance Standards

Commentary: As mentioned above, ISO provides two significant water resistance standards for the watch industry, but these are not the only standards used and manufacturers are not required to use ISO Standards to certify a watch's depth rating.

To recap, what we do know is any watch that uses the water resistant/water resist verbiage had to have passed ISO 22810. So if a watch is devoid of even this language, there is probably zero assurance about water resistance - and this scenario most likely applies to the cheapest of cheapo watches.

When it comes to ISO 6425, manufacturers who meet the standard have the option to display the Diver's verbiage, but they aren't required to. Brands such as Seiko and Citizen are primary examples of brands that use the Diver's verbiage on their dials, but if a watch doesn't say Diver's, that does not automatically mean it isn't ISO 6425 compliant.

The reality is, many brands that produce dive watches adhere to their own in-house standards that often meet or exceed ISO 6425 standards. They don't feel the need to label a watch "Diver's" because their reputation precedes itself. A Diver's and a "Dweller's", both bona-fide dive watches:

This applies to many brands ranging on a spectrum of Doxa to Rolex and everything in between. Some German brands like Sinn, for instance, follow a German standard called DIN 8306 which is very similar to ISO [source: https://wornandwound.com/making-a-tool-watch-a-basic-guide-to-iso-din-and-related-industry-standards/].

So there is certainly some variability in design and testing standards. When in doubt, again remember the 2 Rs of RESEARCH and REPUTATION if you're questioning what standards your watch has been tested to.

MYTH #6: Dynamic Pressure (Movement) Adds Significant Amounts Of Pressure On Top Of The Static Pressure Already Being Experienced

Commentary: I will keep this one brief because there are some major smarty-pants out there that have already done the math to thoroughly debunk this claim.

Quick background: static pressure refers to the amount of pressure experienced when the watch isn't moving, and dynamic pressure is the amount of pressure experienced when the watch is moving. When watches are tested, it is done in a static environment. This has led to the myth that you can't trust the depth rating on a watch because it was tested in a static environment but will be used in a dynamic environment (moving around in the water).

The reality is yes, dynamic pressure can be higher than static pressure, and its effect is exaggerated the deeper you go. That said, the pressure added by movement is negligible at best due to the limits of how fast human beings can move, especially underwater. The result is that dynamic pressure effectively does not impact the depth rating of a watch, especially one that has been tested at over 100% of its depth rating.

EDIT: Thank you to @florincccc for bringing up the topic of water sports in the comments. This is related to the dynamic pressure discussion but really has to do with shock damage. In water sports where you're moving at a fast speed and are prone to falling into the water, the shock of a watch hitting the surface of the water at high speed could certainly cause damage to a mechanical movement, spring bars, or potentially compromise water resistance. ISO22810 does not require a shock resistance test. ISO 6425 does, but it is only done at 4.43 m/s (9.61 mph or 15.5 km/h).

My off-the-cuff piece of advice (just my view, do as you please) is that for water sports that have this risk, either don't wear a watch or wear a quartz/solar watch which will have improved shock resistance. Preferably, wearing a NATO, fixed lugs, or a one-piece watch (such as G-Shock) will also protect against spring bar failure. Or if you're really extreme, some brands like Sinn produce oil-filled watches (always quartz) which are exceptionally shock-resistant.

Here are 4 links that all contain the math behind this, two are forum posters, one is a Hodinkee article in simpler terms, and the last one is the 2nd part the Long Island Watch series from Marc on water resistance - go to the 18:25 timestamp to specifically hear about dynamic pressure, although the full video is definitely worth the watch as he covers ISO standards really well.

https://www.watchuseek.com/threads/water-resistance-myth-vs-reality.239664/

https://www.watchuseek.com/threads/sigh-myth-busting-again.610734/

https://www.hodinkee.com/articles/what-dive-watch-depth-ratings-really-mean-and-whether-you-can-trust-them

https://www.youtube.com/watch?v=-5NjrGPBEKs&list=LL&index=2&t=317s

MYTH #7: Watches Can Never Be Used In Hot Environments Such As The Shower, Hot Tub. Etc.

Commentary: A disclaimer first: I am not trying to tell you what to do with your watch in the privacy of your own shower 😂

Here's the deal. If a watch meets ISO 22810 or ISO 6425, or meets in-house or other standards similar to these, it almost certainly means it has undergone a temperature shock test. A temperature shock test for ISO 22810 involves submerging the watch in 40°C (104°F) for 5 minutes, followed by 20°C (68°F) for 5 minutes, and then again at 40°C (104°F) for 5 minutes. This is to ensure that the gaskets maintain a seal despite expansion and contraction from drastic and rapid temperature changes (just remember, ISO 22810 only tests a sample of watches, not every watch). For ISO 6425 standards, the test involves submerging each and every watch in 40°C (104°F) for 10 minutes, followed by 5°C (41°F) for 10 minutes, and then again at 40°C (104°F) for 10 minutes. [Source: https://www.watchprosite.com/horological-meandering/here-s-the-iso-standard-for-water-resistance/17.1281476.10820301/].

And think about it, water resistant watches and in particular dive watches are designed to be used in harsh environments with temperature changes, such as transitioning from cool water to hot, humid air. OF COURSE the manufacturers have accounted for expansion and shrinkage of gaskets as part of the water resistance equation and design.

So with this logic in mind, it stands to reason they will also survive a trip to the shower or hot tub.

HOWEVER: water-resistance is only as good as the condition and quality of the gaskets. And if you are constantly subjecting your watch to the wear-and-tear of the shower, hot tub, or even just regular use in water, THE PARTS WILL WEAR OUT FASTER. It is no different than someone who drives their car very hard versus someone with a softer touch...the hard driver will need more frequent service.

So use your watch however you want. Just keep in mind that the more wear-and-tear you put on it, the more frequently you will want to have the watch serviced/tested for water resistance (my opinion).

A small note on soaps and chemicals. This is all my personal opinion; do as you wish. I don't think it's bad to subject your watch to gentle soap once in a while for cleaning purposes, or to chemicals you might find in the pool/hot tub for an occasional dip. That said, all of these chemical agents may have the potential to degrade the gaskets faster, or break down the gasket lubricant quicker than normal. In the case of soap, scum might develop over time if you use it a lot. Just consider this all as additional wear and tear that might necessitate shorter service intervals.

MYTH #8: I Can Take My Vintage Watch Into The Water

Commentary: This is the last myth to bust today! The short answer is no, don't take your vintage watch in or near water. Chances are, the parts are past their useful life of assuring water resistance. Plus, if the watch is damaged, original replacement parts might be difficult, expensive, or impossible to obtain. If you absolutely insist on bringing your vintage watch into the water, my personal recommendation is to have it thoroughly inspected and tested by a watchmaker before doing so and adhere to their advice or proceed at your own risk!

And that is all from me! I'm exhausted.

So we can safely say that this post puts all debate about water resistance to rest, right? 😂 In all seriousness, I appreciate if you read until the end and please do chime in via the comments if you think I have missed a major myth or made a factual error!

@Mr.Dee.Bater I imitated the very successful long-form post + memes + gifs format that you often use, so hopefully this has similar effect!