I’m going to address some urban myths related to wristwatches.
For this first part, I’ll talk about two myths concerning waterproofing.
“If you move your hand in water or underwater, it puts tremendous pressure on the watch.”
This is a well-known myth in both the East and the West. The origin of this idea is unclear, but it’s likely a piece of folklore passed down from the days when waterproof performance was far inferior to today.
The reason I mention both the East and the West is that you can even find this misconception on Wikipedia.
From a physics standpoint, it’s quite simple to explain.
For a skilled swimmer, the pressure exerted by hand movement underwater would be around 0.5 atm (51 kPa, which is roughly equivalent to a depth of 5 meters). For the average person, it would be even lower.
Sometimes people claim that moving your hand in water generates pressure of 1 atm or even 2 atm, but that’s an exaggeration beyond human capacity — we’re not talking about the Hulk here. The number might seem small, but 1 atm is actually a significant amount. (1 atm equals the force of a column of air around 1,000 km high pressing down on a surface of 1 square meter.)
For context, even depth gauges and dive computers worn by divers measure water pressure. If this myth were true, the needle of the depth gauge would fluctuate wildly every time someone moved their hand.
“My watch is rated for 200m, but someone said it can handle 300m of water resistance.”
That’s correct. It’s not just your watch; many are designed this way.
A 200m water resistance rating guarantees protection up to that depth, but it doesn’t necessarily indicate the maximum limit. Particularly with ISO 6425 standards for dive watches, tests are conducted to 125% of the stated depth rating. So, this figure represents the minimum guarantee, not the absolute limit. Watches that are not certified under the “Diver’s xxxM” label but instead adhere to in-house standards are often tested even more rigorously than ISO 6425 demands. It’s worth checking these standards to debunk more myths like this one when you have time.
(Note: Getting an ISO certification takes a significant amount of time and money. If you see a watch labeled “Diver’s xxxM” on AliExpress or a Chinese microbrand, it’s likely not legitimate. This is one of the reasons I stopped buying from microbrands.)
A similar misconception occurs with power reserve.
When you see 48 hours, 80 hours, or even 8 days indicated, those are minimum guaranteed times. In reality, the watch may run longer.
Some might say this only applies to dive watches, but if you’re moving your hand with a dive watch and generating around 0.5 atm of pressure, it’s unlikely that just wearing a regular watch and moving your hand would suddenly create 1 atm of pressure.
The waterproofing methods and testing procedures are identical, though the standards differ slightly. Therefore, it’s reasonable to think of them as the same.
I hope these myths are now debunked!
