Watch Water Resistance Explained

Let’s address some of the misconceptions around depth and water resistance ratings in wristwatches. When you look at the caseback of your favourite dress watch and see that it says “30m / 3 Bar / 3 ATM” you’d be forgiven for thinking that it means you can take the watch to a depth of 30m underwater. Unfortunately, that would be an expensive mistake. In reality 30m underwater is incredibly deep – the recommended maximum depth for conventional scuba diving is 40m – and would require a dedicated diving watch with a water resistance much higher than 3 bar. Here then is watch water resistance explained and the answer to “can I swim with my wristwatch?”

Where do the numbers come from?

As mentioned in the introduction, it’s understandable to see a 30m water resistant watch and assume that it’s water resistant to a depth of 30m and it’s baffling that this isn’t the case. The problem is that the vast majority of watches don’t have their water resistances tested in real life. It wouldn’t exactly be practical for Omega to dump thousands of Seamasters into the ocean and see what survives. Instead, they’re (sometimes not so) rigorously tested in a factory – and often without even getting wet.

Air pressure is used instead of water and while in theory that makes sense because depth and pressure are related, it doesn’t account for the difference in medium between air and water. The water resistance rating on your watch is more accurately described as a pressure resistance rating, which is why it’s measured in bar and atm (atmosphere).

The main issue with this is that people fail to account for the fact that underwater the mere act of moving increases the pressure on your watch tremendously. Essentially, your watch’s water resistance rating is its limit when static, so when you introduce movement the depth it can operate safely at is dramatically reduced. Perhaps if you’re lying static at the bottom of your pool your vintage Vacheron will be fine, but it likely won’t survive on the way back up. The question is, if 30m doesn’t mean 30m, then what does it mean?

Well, rather infuriatingly, there’s no one size fits all answer. It varies from watch to watch given different constructions, materials and how they were originally tested – if it’s something you’re desperate to know, you’ll have to check the reviews or contact the brand. But in the short term there is a general rule of thumb to follow, and it goes like this:

30m / 3 Bar / 3 ATM – Splashes

Any watch with a water resistance rating of 30m or lower should avoid anything more than a little splashback from washing your hands. Even then you’d really want to avoid this watch touching water at all. You can essentially look at a 30m resistance watch and know that no efforts were made to adapt it for the water, which is not to say they aren’t well made watches, they just had different priorities. No one is saying that the Vacheron Constantin Traditionnelle Tourbillon Retrograde Date Openface is a bad watch because it only has 30m water resistance.

50m / 5 Bar / 5 ATM – Showers

At 50m you might be able to just about shower with your watch and not have to worry about getting caught in a sudden downpour. These watches tend to be a bit more robust even if they’re still not designed to come in contact with water regularly. Watches like the King Seiko 6L are the perfect example, bold and dynamic but very much a land-based timepiece.

100m / 10 Bar / 10 ATM – Swimming

Hooray, with 100m water resistance you can actually start swimming with your wristwatch. I’d still advise you to stick to pools and controlled environments to stay on the safe side. But let’s be honest in those situations it’s probably safer still to leave it in a secure locker. As for the kinds of watches you can expect, there are literally thousands because this is the most common rating in modern watchmaking.

You’ll even start to find watches that call themselves dive watches at 100m but take that with a pinch of salt. If you want a robust watch with 100m water resistance you’re probably better off looking at field and adventure watches which are designed to survive all conditions – trekking through the jungle and falling in the river kind of stuff.

200m / 20 Bar / 20 ATM – Snorkelling

At 200m you can finally head to the ocean but you should probably stick relatively near the surface with activities such as snorkelling and free diving. 200m is also when you begin to get into the region of ISO rated diving watches that have been officially tested and certified for use in water. ISO ratings also look at other aspects of watchmaking that can affect a watch’s performance underwater, such as condensation and anti-magnetism. These are your entry level divers like the Nivada Grenchen Antarctic Diver.

300m / 30 Bar / 30 ATM – Scuba Diving

If you want to play it as safe as possible, it’s better to say that a watch is a proper diving timepiece at 300m, although even then there’s some debate. Admittedly that debate is less about what depths these watches will survive at and more about what kind of engineering fail-safes and legibility you might need. After all, who cares if a watch survives if you can’t even read the thing when you need it? But that’s getting off topic and watches with 300m water resistance ratings are generally suitable for everything the average human might want to get up to underwater. These are your versatile diving watches like the Tudor Black Bay Fifty Fathoms or Zodiac Sea Wolf.

600m / 60 Bar / 60 ATM – Saturation Diving

Once you go past 300m the number of watches with each specific water resistance rating become a lot less common. When you hit 600m like the recent Grand Seiko 60th Anniversary Limited Edition Professional 600M or Doxa SUB 600T we’re in the realm of saturation dive watches – people who spend their lives under the waves. But then, if you’re the kind of person that regularly goes that deep then you’re probably only using a watch as a last-chance backup anyway. Still, it’s good to know it’s a backup that works.

1,200m+ – Seriously Deep Diving

Now we’re getting to the kind of depths that in real life no watch actually needs or will ever use. Beyond 1,200m the notable milestones are the Ralf Tech Beast (3,000m) and the Omega Ultra Deep (6,000m) that feature insane degrees of water resistance for your horological bragging rights.

Of course, if you really want to show off some serious water resistance, there’s no other choice than the Rolex Deepsea Challenge (11,000m). It’s a timepiece inspired by a concept watch that physically went to the deepest parts of the world’s oceans so if you want a definitive answer for a watch you can swim with, it would be this one. You genuinely cannot get any deeper on Earth. Although, it’s worth keeping in mind that while it might be the most water resistant watch on the market, there’s no such thing as a waterproof watch.