Regardless of what anyone might think of a diver's watch, watches are not legally permitted to use the term "waterproof." The term "water resistant" refers to all watches that can withstand immersion in water – and there is a lot to know about this term!

Let's get this out of the way – no watch can withstand being submerged in water indefinitely, and some can only function at certain depths. It could be the best Seiko diver there is – if it goes too deep – the pressure will cause water to flood the case.


A Rolex undergoing a physical exam. Source: Bob's Watches


The term "water resistant" is used whether you wear a Rolex Submariner or Deep Sea, Seiko's SKX007, or any other kind of watch. In fact, there are some specific reasons why Seiko modders need to understand water resistance, and what parts to use if they plan on diving with their modded Seiko.


What is a Water Resistant Watch?

Whether you're a scuba diver planning a beach trip, or simply curious about water resistance, we would love to give some essential ideas and safeguards to keep your watch safe and secure for years to come.


Source: Wikipedia


A watch with the word "Water Resistant" on it is humidity resistant. It can withstand a few splashes of water from washing your hands or getting caught in the rain.

Water resistance, on the other hand, does not imply that you should swim or shower with your watch on. To immerse a watch in water, it should be rated to a given depth, and be ready to stand up to water pressure.


How is Water Resistance Measured?

One of the most important characteristics and specifications offered by watch brands is water resistance. It's good to be able to wear a watch to the pool or beach without having to remove it before going for a dip.

The issue is that your 30-meter water resistant watch may not be capable of actually withstanding depths of 30 meters. Most watchmakers don't even want you to submerge that 30-meter timepiece at all. Depth ratings aren't always taken at face value in the realm of water resistant watches.

After all, 30 meters below the water's surface is fairly deep, and you're probably not going to be swimming down there without some gear on.


It should have been abbreviated as IOS but Apple got to that first. Source: Pharma Guidances


The International Organization for Standardization (ISO) sets the principles for water resistance ratings, with two independent standards for underwater performance of timepieces: ISO 6425 for dive watches and, as of 2010, ISO 22810 for everything else.

Specific criteria for assessing pressure resistance, a condensation test that follows pressure testing, immersion and temperature shock testing, and more are all things that a diving watch must pass before it can be considered a "diver".


A watch must be water-resistant to at least 100m, among other things, to be ISO-certified. This does not mean that they are automatically Diver's watches though. Source: ioomobile


More importantly, while most of these tests are often done on a tiny sample of the entire production run, pressure testing is required for each watch that receives ISO 6425 certification.

As a result, a watch that can be worn at extreme depths is feasible, and some diver's watches have been known to exceed their ratings in some situations. Seiko, for instance, strapped two 1,000-meter dive timepieces — one quartz, the other mechanical — to a Remotely Operated Underwater Vehicle in 2014.


Imagine strapping a watch on this thing just to test water resistance. Source: Researchgate


The quartz diver worked until it reached 3,248 meters, while the mechanical diver worked until it reached 4,299 meters.

However, ISO 22810 is a little different, and the differences between a genuine diving watch and a water resistant watch are astounding. The standard does not prescribe a specific depth rating for timepieces; rather, it establishes requirements for water resistance testing.

The goal is to eliminate any uncertainty about what you can and can't do with a watch in water and establish a uniform technique for testing water resistance. That said, the manufacturer retains a large amount of discretion in testing.

Unlike ISO 6425, pressure testing is only required on a sample of the production run to meet the standard.

Furthermore, rather than employing water immersion for pressure testing, a manufacturer can use an air chamber, and therefore the minimum pressure testing period for a watch is barely 10 minutes while dive watches under ISO 6425 are tested for approximately 2 hours.



The SKX007 is the most modded watch – and almost, if not everyone in the Seiko community is aware of its specs. It says right there on the dial: “Diver’s 200M”. We’ve seen everywhere (whether it be forums, watch blogs, or online shops) that this model is ISO certified.

But is it really?

Seiko has never confirmed or mentioned the SKX007 to be ISO certified despite it being one of the selling points of the watch. Individuals in the community claims that it meets the standards of the certification, but whether Seiko has applied for and received approval from the ISO themselves, will remain as speculation.


Water Resistant v. Waterproof

The truth is that no watch can be truly waterproof!

A watch's ability to withstand water pressure is always limited. The term "waterproof" means that a watch will not leak under any circumstances, implying that liquid will not penetrate the case and enter the movement.

Waterproof watches are frequently assumed to be completely impervious to water, but this is not always the case. Water damage will affect waterproof watches over time if they are repeatedly exposed to water.


How do you let people know that a watch is water resistant? Put the ocean behind it. Source: Seiko Watches


Water resistant indicates that the watch is can safely come in contact with water, but this is not a universal rating. In fact, many watches have different water-resistance ratings, which determines what you can safely do with the watch.

Water is a watch's worst enemy (except for maybe shock). If you swim or participate in water sports, you should have your watch checked for an accurate reading of its water resistance levels at least once a year. Watches need to be well maintained to be water resistant, which is important to know for watch modders.


Wet and Dry Water Resistance Test

Water resistance technology has advanced substantially in recent decades.

With the advancement of technology, there is a greater need to test your watch's water resistance, and not assume it is ok to do whatever you want in the water.

This isn't surprising given that gaskets, which are an important component of water resistance, naturally degrade over time.

You don't want to go to the beach with your valuable dive watch only to discover, in the worst possible way, that the gasket has failed. That is why many watchmakers carry a water tester in their arsenal.

With that in mind, it's important to understand that the water resistance test isn't rocket science. It's simply putting strain on the watch to see if it can withstand it. Water resistance tests are classified into two types: dry tests and wet tests.


An example of a dry testing machine. Source: Rolex Forums


A vacuum tester is used to measure the amount of warping of the crystal in a vacuum chamber during a dry test, also known as an air test. In general, a dry test is safer because no water is involved.

However, it cannot specify the level of pressure used and can only demonstrate that a watch is airtight to a certain extent. As a result, it is best understood as a test to see if there are any leaks.


A common design for a wet WR test. Source: Rolex Forums


Wet testing, on the other hand, is performed with a pressure tester by first pressurizing the chamber before submerging the watch in water, and then depressurizing the chamber while the watch is submerged in water.

Any leaks are revealed by bubbles of air escaping from the watch. Following the wet test, a condensation test can be performed. After heating the watch, a cold drop of water, or ice, is placed on the crystal.

If any water got into the case during the previous wet test, it will show up as condensation on the underside of the crystal. As a consequence, wet testing can specify the amount of pressure applied to the watch but can result in water damage if performed incorrectly.


Important Watch Components for Water Resistance

Your watch is vulnerable to water in three main places: the crown, caseback and any gaskets. Understanding the watch parts at these points will ensure that your watch is as water resistant as possible.


The crown is an important factor in ensuring water resistance, and unlike the other parts, it can be left open by mistake!

The crown-stem hole is the weakest point in a watch for water to enter. It is connected to the movement via a hole in the case edge. The gasket is constantly compressed, chafed, and stressed as the crown is constantly moved to different positions, wound, and turned to correct the time.



Screw Down Crowns are threaded and screw into a casing with a matching threaded tube. When the crown is tightened, a gasket compresses and seals the opening, guaranteeing that the crown is water resistant.

A screw-down crown is a must-have feature for any watch that will be worn when diving.

Our NamokiMODS SKX007 Crown premium triple-gasket (that's right, 3 GASKETS compared to the factory SKX crown which has a single gasket) threaded screw-down SKX crown which has passed a 200m pressure test is a great addition to your SKX007 mod.

It is constructed from surgical grade 316L Stainless Steel, and when properly installed, would allow your SKX to be used for just about any kind of diving.


A caseback can be fastened to a watch in a few different ways.

Snap-on casebacks are the least water resistant because they are sealed by pressure. With our SKX007 Sapphire display Caseback, you can see the workhorse movement ticking away within your Seiko dive watch. Like all of our other casebacks, it has been tested to a depth of 200 meters.



At NamokiMODS we stock loads of SKX007 mod parts and a variety of different SKX007 cases and casebacks. Some of our casebacks are more suited for desk diver builds, like our slim SKX007 caseback. In exchange for a lower water resistance rating, this caseback allows for a much slimmer watch profile with its reduced thickness.

If you have any questions about a specific part, and whether or not it will be ok for a diver's watch that will be used for diving, check the description, or just send us an email with your questions!

We are happy to help!


Gaskets, often called "O" rings, are watertight seals used at the joints where the crystal, caseback, and crown meet the watch case. They are composed of rubber, nylon, or Teflon. Gaskets deteriorate and break down with time, reducing a watch's water resistance.



Water resistance should be tested on your watch once a year, and watch maintenance will be required to ensure ongoing water resistance.

Any qualified watchmaker should have the basic equipment required to test the watch, and the cost should be low. If you need any replacement gaskets for your SKX007, NamokiMODS has everything you need!


How to Maintain Water Resistance?

Water resistant watches should be pressure tested once a year if they are to be used in the water. In addition, every two or three years, the seals should be replaced. Due to hot water issues and the fact that soap can act as an abrasive, showering or bathing with your watch on can be harmful for it.

If you like to take a bath or shower with your watch everyday – plan on getting it tested every six months for water resistance, and having it rebuilt with new gaskets every two or three years!

Seiko mods are a great way to take iconic Seiko designs, and make them your own. At NamokiMODS we create aftermarket Seiko mod parts that are at least up to OEM standards – if not better. When you buy skx007 mod parts from NamokiMODS, you can be sure that you are getting amazing quality at a very reasonable price.

Make sure to be aware of how water resistance works – and what you need to do to protect your investment. We have everything you need to keep your Seiko skx007 in tip-top shape – so please think of us when you need aftermarket Seiko mod parts.

July 26, 2021 — Jeremiah A


Mark Christenesen said:

Need to restore water resistance to a ratio II freediver clone of a skx007. What do I need?

Leave a comment

Please note: comments must be approved before they are published.