How to Read Watch Water Resistance Ratings — A Complete Guide
Watch Guide
Most watches carry a water resistance marking, but reading it correctly is a different matter. The number stamped on a caseback or dial tells you the static pressure the watch was tested against in a lab — not the depth you can safely take it to. This guide explains what the ratings mean, where to find them, and which LOBOR watches suit each level of water activity.
Step 1: Find the Water Resistance Marking
Check the caseback first. Most watches engrave the water resistance rating there. Some also show it near the 6 o'clock position on the dial.
If there is no marking at all, treat the watch as having zero water resistance. That means no rain, no handwashing, no sweat exposure if you can help it.
Step 2: Understand ATM, BAR, and Metres
Three units show up on watch specs: ATM, BAR, and metres. They all measure the same thing. ATM and metres are the most common. BAR appears occasionally but is equivalent to ATM. Here's how they convert:
| Unit | Full Name | Conversion |
|---|---|---|
| ATM | Atmospheres | 1 ATM = 1 BAR ≈ 10 M |
| BAR | Bar (pressure) | 1 BAR = 1 ATM ≈ 10 M |
| M | Metres | 10 M = 1 ATM = 1 BAR |
Water Resistance Level Guide — LOBOR Model Reference
The table below maps each water resistance level to real-world use, with the corresponding LOBOR collections. As a general rule, pick a rating one level above what you actually plan to do — it gives you a practical safety margin.
| Water Resistance | ATM | Suitable for | Not suitable for | LOBOR Collection |
|---|---|---|---|---|
| 30M | 3 ATM | Splash resistance, handwashing, light rain | Swimming, shower | HERITAGE, CELLINI, DYNASTY, BELFRY |
| 100M | 5 ATM | Daily water exposure, rain, light splashes | Swimming, showering, water sports | PLANETARIUM |
| 200M | 10 ATM | Swimming, snorkeling, water activities | Deep diving | MARINUS |
5 Things to Know About Watch Water Resistance
The rating number is not a safe diving depth
A 30m rating does not mean the watch is safe 30 metres underwater. The number reflects static lab pressure. Real-world movement — a fast wrist stroke, a dive entry — generates dynamic pressure that can exceed the rated limit significantly.
Heat and steam degrade seals faster than cold water
Rubber gaskets expand and contract with temperature changes. Hot showers, saunas, and hot springs accelerate this degradation. Even a watch rated for swimming should avoid prolonged heat exposure.
Never press buttons or pull the crown underwater
Operating any pusher or crown while submerged breaks the seal immediately and allows water into the movement. The damage is often permanent. If your watch has pushers, make sure any timing function is set before entering the water.
Battery replacements require a proper reseal
When a battery is replaced, the caseback seal needs to be properly reseated and tightened. An uneven or incomplete seal compromises water resistance entirely. Having the battery replaced by a professional watchmaker avoids this risk.
Leather straps are not water-resistant
A water-resistant case paired with a leather strap is still a problem near water. Leather absorbs moisture, stiffens, and deteriorates with repeated wetting. Swap to a rubber or silicone strap before any water activity.
What is a Screw-Down Crown?
A screw-down crown is the little knob on the side of a watch that you twist to lock it into the case. It sounds like a small detail, but it actually helps improve water resistance by tightening the seal and keeping dust or moisture out.
Compared to a normal push-pull crown, you’ll need to unscrew it first before you can set the time or date. After you’re done, you just screw it back in. Nothing complicated, but it’s an extra step that helps the watch stay better protected.
You’ll usually see this kind of setup on dive watches. The LOBOR Marinus is one of them. It’s designed with water in mind, and the screw-down crown is one of those practical details that makes it more reliable in real everyday use.
If you’re interested, you can check out our guide: Dive Watch: The Ultimate Guide for Watch Enthusiasts.
📖 Dive Watch Guide The Ultimate Guide for Watch Enthusiasts →Frequently Asked Questions (FAQ)
Any watch rated 30m / 3 ATM or above handles handwashing fine. Use cool or lukewarm water and dry the case gap afterward. If there's no water resistance marking on the watch at all, take it off first.
A 5 ATM (50M) watch is suitable for everyday water exposure such as handwashing, rain, and light splashes. Some users may also wear it in situations where there is brief contact with water, but it is primarily designed for daily water resistance rather than extended exposure to water. It is generally not recommended for showering or prolonged use in wet environments. Models such as the LOBOR Planetarium fall into this category, offering basic protection for everyday wear.
Stop pressing buttons immediately. Place the watch face-up and away from heat. Bring it to a service centre as soon as possible — the longer water sits inside a movement, the more damage it causes.
Yes. Seals and gaskets degrade with age, heat, and repeated water exposure. A watch rated 5 ATM when new may offer less protection after a few years of heavy use. Regular seal checks by a watchmaker are worth doing if the watch goes near water often.
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