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Water resistance is one of the most misunderstood specifications on a watch. The numbers on the caseback or dial do not mean what most people assume. This guide explains what ATM ratings actually mean, what activities each rating covers, how sealing works, and how to maintain water resistance over time.
What Water Resistance Actually Means
Water resistance in watches is measured in ATM (atmospheres), bar, or meters. These numbers represent the static pressure the watch can withstand in laboratory testing, not the depth you can take it to in real use. A watch rated at 30m does not mean you can take it 30 metres underwater. It means it can withstand static pressure equivalent to 30 metres of water in controlled testing conditions.
The reason this matters: pressure in water increases with depth, but activity in water also creates dynamic pressure that significantly exceeds the equivalent static rating. A person swimming creates more pressure on their watch than simply being submerged at the equivalent depth. This is why the practical limits of each ATM rating are considerably more conservative than the stated depth equivalents.
Water resistance is achieved through three sealing points: the caseback gasket, the crystal gasket, and the crown seal. Every one of these must hold for the watch to maintain its rated resistance. The weakest point determines the effective rating.
ATM Ratings Explained
| Rating | Static Equivalent | What It Covers | What It Does Not Cover |
|---|---|---|---|
| No rating | None | Dry conditions only | Any water contact including rain |
| 1 ATM / 10m | 1 bar | Accidental splashes only | Hand washing, rain, swimming |
| 3 ATM / 30m | 3 bar | Rain, hand washing | Swimming, showering, sustained contact |
| 5 ATM / 50m | 5 bar | Swimming, snorkelling, showers | Diving, water sports, high-pressure water |
| 10 ATM / 100m | 10 bar | Swimming, snorkelling, surface water sports | Scuba diving below 40m |
| 20 ATM / 200m | 20 bar | Recreational scuba to 40m | Professional diving, saturation diving |
| ISO 6425 diver | Certified | Scuba diving with safety margin | Saturation diving |
The Three Sealing Points
Caseback Seal
The gasket between the caseback and case body is the primary water resistance component. Screw-down casebacks, which thread the caseback against the case body rather than relying on a press fit, provide more reliable compression and are standard on any watch rated above 3 ATM. The Söner Nostalgia uses an arched screw-down caseback that follows the wrist contour while providing the sealing force needed for 5 ATM.
Crystal Seal
The gasket between the crystal and case bezel must seal across the full perimeter of the crystal. On rectangular watches, this gasket must maintain compression across four straight edges and four corners, which is more demanding than sealing a round crystal. Quality rectangular watches use precision-fitted gaskets rather than standard round gaskets adapted to a non-round shape.
Crown Seal
The crown is the most common ingress point on any watch. O-rings around the crown stem compress when the crown is pushed in. For ratings above 5 ATM, a screw-down crown adds a threaded cap that provides additional sealing force. The crown must always be fully pushed in and locked before any water contact.
Söner Water Resistance by Collection
All Söner watches are tested for their stated ratings before shipping. The 5 ATM rating on the Nostalgia, Amorous, and Legacy collections has been specifically verified for swimming and snorkelling use, not just splash resistance. The Momentum at 10 ATM is rated for active water sports and surface swimming. For the specific engineering behind water resistance in rectangular cases, see our guide to rectangular watch water resistance.
The Nostalgia and Amorous use arched screw-down casebacks. The Momentum uses a screw-down caseback with a screw-down crown. All four collections use sapphire crystals fitted with precision gaskets.
The important caveat: Water resistance ratings are tested at the time of manufacture. Gaskets age, chemicals degrade rubber, and physical wear affects seals. A watch that was 5 ATM when new may be less water resistant after three years of daily wear without a seal inspection. If you swim with your watch regularly, have the seals checked every two to three years during servicing.
How to Maintain Water Resistance
Protect the Seals
- Rinse with fresh water after sea water or chlorine exposure
- Avoid extreme temperature changes (sauna then cold pool)
- Keep chemicals including perfume, sunscreen, and cleaning products away from the case
- Never operate the crown underwater unless screw-down
- Always ensure the crown is fully pushed in before water contact
Service Schedule
- Have seals inspected every 2 to 3 years if you swim with the watch regularly
- Any time the case is opened for battery or service, new gaskets should be fitted
- After a knock or impact near the caseback or crown, have seals checked
- If moisture appears inside the crystal, take the watch to a watchmaker immediately
- Never have a water-resistant watch opened by a jeweller without watchmaking experience
Frequently Asked Questions
What does water resistant mean on a watch?
Water resistant means the watch can withstand water ingress up to a specified static pressure, measured in ATM or bar. The number does not equal the depth you can take the watch to in real use. A 5 ATM watch covers swimming and snorkelling. A 3 ATM watch covers rain and hand washing. A 10 ATM watch covers active water sports and surface swimming.
Can I shower with a 5 ATM watch?
Yes. 5 ATM covers showering, swimming, and snorkelling. The Söner Nostalgia, Amorous, and Legacy collections are all rated at 5 ATM and have been specifically tested for swimming and snorkelling use. Avoid exposing any watch to hot showers or saunas repeatedly, as extreme heat accelerates gasket degradation over time.
Can I swim with a 3 ATM watch?
No. 3 ATM covers rain and hand washing but not sustained water contact or submersion. Despite the 30m depth equivalent in the rating name, the dynamic pressure created by swimming exceeds what a 3 ATM watch is designed to handle. For swimming you need at least 5 ATM.
How often should I have my watch's water resistance checked?
Every 2 to 3 years if you regularly expose the watch to water, or any time the case is opened. Gaskets dry out and lose elasticity over time. A watchmaker can pressure-test the case and replace gaskets during a service. This is particularly important for watches used in sea water or chlorinated pools where chemical exposure accelerates seal degradation.
What is the difference between water resistant and waterproof?
No watch is truly waterproof. The watch industry stopped using the word "waterproof" decades ago because it implies absolute protection that no sealed watch can guarantee. "Water resistant" correctly communicates that the watch resists water ingress up to a specified pressure, under specific conditions, with properly maintained seals. All resistance ratings have limits and all seals age.
All Söner rectangular watches carry a minimum 5 ATM water resistance rating, tested for swimming and snorkelling. The Momentum is rated at 10 ATM. Sapphire crystal, 800HV hardened steel, 10-year international warranty. From $385.
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