Jamie Weiss
“How waterproof is my watch?” is a very common question asked here at time + tide. And the short answer is… not waterproof. There is no clock on Earth that can withstand the absolute pressure of Mother Nature. No, watches are water resistant at best, regardless of marketing. Certainly, there are no brands that claim they will make completely waterproof watches. That’s not possible (and it’s illegal to argue that I might add).
Importantly, the water resistance rating printed or engraved on the meter or feet of the watch’s dial or caseback is not literally. But they show something and continue to be one of the most important aspects of the watch. It’s a particularly relevant topic to discuss recently, as some brands, such as Patek Philippe and Richard Mille, have dramatically downgraded the water resistance ratings of some watches, leading some consumers to scratch their heads.
So with that in mind, we thought we would break down the most commonly cited water resistance ratings found on you and the watch, so that the watch would not change into a container for storing H2O, and share it with you…
What does the water resistance rating actually mean?
First of all, you might be asking: why do watches say they are water resistant to certain depths when they are not? It relates to how watchmakers test their water resistance. Simply put, laboratory conditions never equal real-world outings, and for several reasons.
Most water resistance tests performed by watchmakers are dry or “static” tests, with no water at all. Usually, the clock is placed in a high-pressure chamber, where the air pressure increases, and the clock is measured for leaks and deformation. Even if the watch is not touching the watch, it is said to be water resistant. Even in actual water testing, the clock is usually slowly immersed in water under very controlled conditions.
But when you wear a watch, you are still or not moving slowly. For example, when swimming on a clock, you repeatedly sink and float the clock, exposing it to a wide variety of external pressures. Rapid fluctuations in pressure (and other factors such as temperature changes, water in motion, and G-force) can affect the water resistance of the watch.
What are the key points for these ratings? Well, they still help consumers get rough indications of how water resistant the watch is. Many brands also keep their watches water resistant rather modest. Panerai, for example, actually tests watches at 125% of their natural water resistance rating. And I mentioned Patek before – I think the massive water-resistant downgrade mentioned is more of a symbol of conservatism than anything else… these commonly cited ratings really make sense from those who own (and swim) with enough watches to know.
30m (3 atm/3 bar)
A very common rating between dress watches or high complications is that when the watch says 30 meters or 3 ATM/bar (bar meaning ATM, bar meaning the same thing), it does not mean that it is water resistant to 30 meters below sea level. In reality, it means your watch can withstand small splashes of water from washing your hands or getting caught in the rain…and that’s about it.
It is also essential that you don’t take this small water resistance into the shower and take your watch. Because Steam has an incredibly troublesome habit of going into places that you don’t even imagine. Also another hot tip: if the watch has a leather strap, avoid swimming completely (even if it’s a diving watch and comes with a leather strap… I’m looking at you, Panerai, I’ll talk about mixed messages). Leather straps can deteriorate very quickly with water, especially salt water.
TL; DR: Keep away from water
50m (5 atm/5 bar)
The watch, which is said to be water resistant to up to 50 meters, is roughly the same as the 30 meters. This means that it is not water resistant at all. The same rules apply here for 30 meters. Really: Water splashes are fine, but swimming isn’t. Depending on who you ask, some say it’s a-ok to wear a 50m watch in the shower, but once again, I don’t put it in danger.
Generally speaking, it’s a terrible idea to have any kind of watch in the shower with you who are water resistant to under 200 meters. The heat can ruin the gasket on a watch, and if I’m being honest, wearing a watch in the shower seems like a decisive and stupid idea.
tl;dr: nothing but washing your hands and strolling in the rain
100 meters (10 ATMs/10 bars)
Now things are beginning to get serious. If the clock is rated as water resistant to 100 meters or 10 atmospheres, it can go for a swim with confidence or even go snorkeling. Most recent sports watches are rated at least 100 meters. You can see that watches up to 100 meters usually come with screw-in crowns and screw-in cases.
However, 100 meters does not mean you can go diving 100 meters below sea level while wearing your watch (not that you’re likely to dive deep anyway if you’re not a professional diver). Also, there’s some fun information here. If you’ve ever wondered how a “50 Fathom” works in meters or in the atmosphere, it actually corresponds to 91 m. However, the modern Branpine 50 Fathom is rated at 300 meters.
TL; DR: You can swim together
200m (20 ATM/20 bar)
Once the watch reaches 200 meters of water resistance, it can become a successful diving watch. This means that activities like swimming, surfing, snorkeling and even skin diving are perfectly fine. Watches with this level of resistance are also beginning to see acronyms like ISO (International Organization for Standardization). For example, ISO 6425 is a certification given to diving watches so that they can withstand static submersion at 125% of their water resistance rating.
To receive ISO certification, all works must be tested independently. This is less common as it is a costly movement for watchmakers. However, if the watch has a 6425 certification, it works well in most underwater arenas. However, a 200m resistant watch is not good for saturated diving. To do that, we have to go.
TL;DR: Suitable for surfing and recreational diving
300 meters (30 ATM/30 bar)
Welcome to the big leagues of diving watches: category over 300 meters. It is not uncommon to see a watch that is rated water resistant to over 300 m with a helium escape valve. Developed by Doxa and Rolex in the 1960s, this one-way valve allows the helium caught in the case to escape during decompression as a saturated or mixed gas diver resurfaces from deep diving.
If helium is trapped inside the case and cannot find a way, the pressure inside the case can become too high, causing serious damage to the watch, such as the crystals popping straight out. In short, if the clock is rated below 300 meters, it can be completely problematic in almost any underwater context.
TL;DR: Can withstand most diving conditions
Over 300 meters
Above 300 meters, the water resistance rating is a bit unrelated to the average consumer. It is common to see recent watches being 1,000 meters, even higher, but these are watches that professional saturated divers can actually get used to. There is a high chance that the average watch buyer will compromise this watch’s water-resistant rating, so there is nothing that can prevent it from swimming with the crown.
TL;DR: Professional diving tools
Note: The water resistance of the watch will break down over time
Another thing worth considering is that the watches become less water resistant over time, especially if they are not regularly maintained. The rubber gasket hardens and loses its integrity. The crystals begin to slowly align and become more fragile over time. Therefore, a watch that could have been rated 100m when it was first released could be much less water resistant after 10 or 2 years. Generally, assume that vintage clocks should not be traced back to water. Even vintage sports watches that may have been water resistant to the original.
