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How waterproof is your watch? How waterproof is your watch?

How waterproof is your watch?

Jamie Weiss

“How waterproof is my watch?” is a very common question that we get asked here at Time+Tide. And the short answer is… it’s not waterproof. There isn’t a watch on Earth that can withstand the absolute pressure of Mother Nature. No, watches are, regardless of marketing, water-resistant at best. Indeed, no brand claims they make a totally waterproof watch, as such a thing is nigh-on impossible (and illegal to claim, might I add).

Crucially, the water resistance rating that’s printed or engraved in metres or feet on the dial or case back of a watch, isn’t literal – a mistake many newcomers to our hobby make. However, they’re indicative of something, and remain one of the most important aspects of a watch. It’s a particularly relevant topic to discuss lately as some brands, including Patek Philippe and Richard Mille, have drastically downgraded the stated water resistance ratings of some of their watches recently, leading some consumers scratching their heads.

Patek Philippe Aquanaut Travel Time 5164G WW24
Earlier this year, Patek Philippe quietly standardised the water resistance rating of its Aquanaut range to 30 m down from 120 m, confusing many watch collectors.

So, with that in mind, we thought we’d share with you this simple rule book of sorts breaking down the most commonly cited water-resistance ratings found on watches, to ensure that your timepiece doesn’t turn into a receptacle for storing H2O…

What does a watch’s water resistance rating actually mean?

Glashütte Original SeaQ static test
Glashütte Original SeaQ watches undergoing dry pressure testing.

First of all, you might be asking: why do watches say they’re water resistant to certain depths when they’re not? It’s all got to do with the way water resistance is tested by watchmakers. Simply put, the conditions in a laboratory are never going to be the same as out in the real world, and there are a few reasons for this.

Most water resistance testing undertaken by watchmakers is dry or “static” tests, which don’t use water at all. Typically, a watch will be placed in a hyperbaric chamber and the air pressure increased, with the watch then measured for leaks or deformations. The watches are then said to be water resistant, even though no water has touched the watch. Even tests that actually use water typically slowly immerse a watch into water under very controlled conditions.

Tudor Black Bay Steel water immersion test
A Tudor Black Bay undergoing a water immersion pressure test.

However, when you’re wearing a watch, you’re not staying still or moving slowly. When swimming with a watch, for example, you’re repeatedly submerging and surfacing the watch, exposing it to a wide variety of external pressures. The rapid variation in pressures (as well as other factors like temperature changes, moving water and G forces) can affect a watch’s water resistance.

What’s the point of these ratings, then, if they don’t reflect real-world conditions? Well, they still help consumers get a rough indication of how water-resistant a timepiece is. Many brands also understate the water resistance of their watches (for example, Patek Philippe, as discussed earlier) – although you can’t rely on that while shopping for your average timepiece. Here’s what these commonly cited ratings really mean.

30 metres (3 ATM / 3 Bar)

vacheron constantin historiques cornes de vache 1955 case

A very common rating among dress watches, if your timepiece says 30 metres or 3 ATM / Bar (ATM meaning atmospheres, Bar meaning the same thing) then IT DOES NOT mean it’s water resistant to 30 metres below sea level. In reality, it means that 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 imperative that you don’t take a watch with this little water resistance into the shower with you, because steam has an incredibly nasty habit of getting into places you’d never otherwise imagine. Also, another hot tip: if your watch has a leather strap, avoid swimming with it entirely. Leather straps can degrade extremely quickly in water, especially salt water.

TL;DR: keep away from water

50 metres (5 ATM / 5 Bar)

Audemars Piguet Royal Oak Selfwinding Flying Tourbillon Openworked 41mm Sand Gold 2024 4

Watches water resistant to 50 metres are much the same as 30 metres, which is to say that they are not very resistant to water at all. The same rules apply as 30 metres here, really: splashes of water are fine, but swimming is not. Depending on who you ask, some will say that it’s A-OK to wear a 50-metre watch into the shower, but once again I wouldn’t risk it.

Generally speaking, taking any sort of watch into the shower with you that’s water-resistant below 200 metres is a terrible idea, as heat can also mess with a watch’s gaskets and, if I’m being frank, wearing a watch in the shower just seems like a resolutely silly idea.

TL;DR: nothing more than washing your hands or a walk in the rain

100 metres (10 ATM / 10 Bar)

TAG Heuer Carrera Chronograph Glassbox Panda Solo 1

Now things are starting to get serious. If a watch is rated to 100 metres or 10 ATM of water resistance, it means that you can go swimming with it confidently, or even go snorkelling. The vast majority of sports watches these days are rated to at least 100 metres. You’ll typically find that a watch rated to 100 metres also has a screw-down crown and/or a screw-down case back, which ensures a superior level of water resistance compared to watches that don’t have these features.

However, 100 metres doesn’t mean you can go diving 100 metres below sea level while wearing the watch (not that you’re likely to be diving that deep anyway if you’re not a professional diver). Also, here’s a fun tidbit: if you’ve ever wondered what “Fifty Fathoms” works out to in metres or atmospheres, it’s actually equivalent to 91 m – the modern Blancpain Fifty Fathoms, however, is rated at 300 metres.

TL;DR: okay to swim with

200 metres (20 ATM / 20 Bar)

Watch waterproof guide

Once a watch gets to 200 metres of water resistance, then chances are, it’s a fit-for-purpose dive watch. That means that activities like swimming, surfing, snorkelling or even skin diving are completely fine. Timepieces with this level of resistance are also where we start to see acronyms like ISO (International Organisation for Standardisation). ISO 6425, for example, is a certification given to dive watches that can do things like withstand being statically submerged in 125% of their water-resistant rating.

For a watch to receive ISO certification, each and every piece needs to be independently tested, which is a costly exercise for watchmakers, so it isn’t very common. But if your timepiece does have 6425 certification, it’s going to perform well in most underwater arenas. However, a watch that’s resistant to 200 metres is not good for saturation diving. For that, we have to go, pardon the pun, deeper.

TL;DR: good for surfing and recreational diving

300 metres (30 ATM / 30 Bar)

5019 12B30 64A PROFIL VALVE RVB

Welcome to the big leagues of dive watches: the 300-metre and beyond category. It’s not uncommon at all to see timepieces that are rated to 300 m or more of water resistance accompanied by a helium escape valve. Developed by Doxa and Rolex in the ’60s, this one-way valve ensures that when saturation or mixed gas divers are resurfacing from a deep dive, the helium caught in the case can escape during decompression.

If helium gets trapped inside the case and cannot find a way out, the pressure inside the case becomes too much, and can cause serious damage to your timepiece, including the crystal popping straight off. In short, if your timepiece is rated to 300 metres or beyond, then chances are it’s going to be completely fine in almost any underwater context.

TL;DR: can withstand most diving conditions

Beyond 300 metres

ultra deep

Beyond 300 metres, water resistance ratings become a bit irrelevant to the average consumer. It’s common to see watches these days rated at 1,000 metres and even higher figures, but these are watches that can only really be used to their full capacity by professional saturation divers. There’s nothing the average watch buyer will be able to subject this watch to that’s likely to compromise its water-resistance rating, short of swimming with the crown out.

TL;DR: professional diving tools

Note: a watch’s water resistance degrades over time

Rolex Explorer 1016 Zach Marcus Shot
The Rolex Explorer ref. 1016 was rated at 100 m water-resistant when new, but shouldn’t be swum with in 2024.

The other thing worth considering is that watches become less water-resistant over time, especially if they’re not regularly serviced. Rubber gaskets harden and lose their integrity; crystals start to fit looser and movements become more fragile over time. Therefore a watch that might have been rated at 100 m when it was first released might be far less water-resistant a decade or two later. In general, assume that you should never expose a vintage watch to water, even vintage sports watches that might have originally been water-resistant.