It's a scenario we've seen all too often: a beautiful timepiece ends up on our workbench with a fogged-up crystal because the owner took a "30m water resistant" watch for a quick dip in the pool. It's an easy mistake to make, but it's one that can be incredibly costly.

The truth is that watch water resistance isn't a literal measurement of depth; it’s a measurement of pressure. In this guide, we’re going to pull back the curtain on how the industry tests these watches and, more importantly, how you can ensure your favourite timepiece stays dry.

If you look at vintage watches from the mid-century, you’ll often see the word "Waterproof" stamped on the back. However, since the 1960s and 70s, the industry—led by modern ISO standards—has moved away from this term.

Today, we use the term watch water resistance. Why? Because under enough pressure, any seal can fail. By calling it "resistance," manufacturers are being honest: the watch is built to withstand specific conditions, but it's not an invincible suit of armour.

When discussing watch water resistance, it’s helpful to know that there are two main "rulebooks" manufacturers follow.

Most everyday watches follow ISO 22810. This is a general standard that covers a watch's ability to handle daily life, swimming, and light snorkelling. It's a reliable baseline, but it isn't a "torture test."

For serious professional tools, you want to look for the ISO 6425 "Divers" certification. This is far more rigorous. To meet this standard, every single watch (not just a sample) is tested to 125% of its rated depth. It also involves testing for thermal shock, resistance to saltwater, and even the security of the strap under pressure. If you see "Divers" on the dial, you know the watch water resistance has been verified to a much higher degree.

If you're looking for a timepiece that takes watch water resistance seriously, we currently have some exceptional pre-owned pieces available in our store.

While the gaskets inside the case do a lot of the heavy lifting, the crown is often the first line of defence for watch water resistance. On most high-performance timepieces, especially those rated for 100m or more, you'll find a screw-down crown.

Unlike a standard crown that simply pushes in, a screw-down crown is threaded. When you screw it into the tube, it creates a physical, mechanical seal by compressing internal rubber O-rings. Think of it like a submarine hatch; if it isn't dogged down tight, the vessel isn't watertight.

A high watch water resistance rating on your watch head is only half the battle; you need a strap that can handle a soak without falling apart.

Isofrane: The Professional Rubber Choice

When it comes to pure diving performance, Isofrane is the industry standard. These aren't your typical silicone straps; they’re made from a specialised NBR rubber. They're incredibly soft, hypoallergenic, and resistant to the salt and chemicals that usually perish lesser straps.Explore the Isofrane Collection

Hirsch Heavy Calf: 100m Water-Resistant Leather

Many people believe leather and water don't mix, but the Hirsch Heavy Calf is here to prove them wrong. Part of the Hirsch 100m Water-Resistant range, this strap is tanned in a way that allows it to be submerged and then dried without losing its shape or suppleness. It’s the perfect way to keep a classic look while remaining practical.Explore Hirsch Heavy Calf

Di-Modell Rallye: Sporty Water Protection

For those who love the perforated racing look, the Di-Modell Rallye features a unique "Aero Lining" and a water-protected finish. It’s designed for the active wearer who might find themselves caught in a downpour or needing to rinse their watch after a long day, ensuring the strap stays as fresh as the watch.

It’s a common misconception that once a watch is rated for 100m, it stays that way forever. In reality, watch water resistance relies on tiny rubber O-rings and gaskets. Like any rubber product, these will eventually perish, dry out, or lose their elasticity.

To keep your movement safe, we recommend the following maintenance:

• The 24-Month Rule: Have your watch pressure tested by a professional every 12 to 24 months. This is a quick and relatively inexpensive check that can save you a fortune in repair costs.
• Rinse After the Sea: Saltwater is incredibly corrosive. If you’ve been for a dip, always rinse your watch in fresh, lukewarm water to prevent salt crystals from eating away at the gaskets.
• Avoid Dryness: If a watch sits in a drawer for years, the seals can become brittle. Regular wear and periodic checks are the best ways to ensure your watch water resistance remains intact.

To keep your watch safe, stay vigilant about these common hazards:

• Steam & Humidity: Saunas and hot showers are the number one cause of water damage.

• Chemical Exposure: Perfumes, suncreams, and chlorine can cause rubber gaskets to crack and fail.

• Saltwater: Always rinse your watch after a dip in the ocean to prevent salt corrosion.

• The Crown: Never adjust the time or use chronograph pushers while the watch is wet.

Ultimately, keeping your timepiece dry is about understanding its limits and performing basic maintenance. Here’s what you need to remember: