Reference Guide · Updated on 9 August 2026 · Watch Guide Team

Diving watches: what makes a watch a ‘true diver’ and what doesn’t

The difference between water-resistant and Diver-certified: genuine ATM ratings, ISO 6425 standard, a unidirectional bezel and luminescence that’s actually legible.

Quartz, automatic or manual: which to choose and why

The quartz It is the most accurate and the most practical: it diverts around ±15 seconds per month, it needs nothing more than a new battery every 2–4 years and is more shock-resistant. The automatic It is powered by a wrist movement and deflects between -10 and +30 seconds a day (a COSC-certified calibre has a rate of between -4 and +6), but it is the one with a mechanical soul, a sliding seconds hand and long-term value. The manual It needs to be wound every day and is usually more delicate, which is why it’s used in dress watches. If you’re looking for accuracy, go for quartz; if you’re looking for fine watchmaking, go for an automatic.

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Water resistance: what the ATM rating really means

The figure on the box does not represent the actual working depth; it is a static laboratory pressure reading. In practical terms: 3 ATM / 30 m It can withstand rain and splashes, but nothing more; 5 ATM allows you to wash your hands but not to have a shower (the hot water exceeds that pressure and the heat causes the seals to expand); 10 ATM it’s suitable for swimming; and 20 ATM / 200 m That’s the minimum for diving. If you want a proper diving watch, look for the certification ISO 6425, which can be identified by the word printed on the dial DIVER'S alongside depth.

Luminescence: Super-LumiNova and LumiBrite

Modern luminescent paint is not radioactive: it is a phosphorescent material that absorbs light and gradually releases it. Super-LumiNova (Switzerland) and LumiBrite (Seiko) are the models, with variants such as the bluish BGW9 or the greenish C3, which is the one that shines the brightest. What makes the difference in practice is not the paint brand but the layer thickness: that’s why a €150 Seiko can outshine a €1,500 Swiss watch. With diving watches, check that the bezel at 12 o’clock and the minute hand – which is the one that counts underwater – are also luminescent.

Steel, titanium and coatings

The standard is the 316L steel, surgical grade, corrosion-resistant and easy to polish. The 904L (which Rolex calls Oystersteel) is slightly more corrosion-resistant and produces a denser polish, but the difference in everyday use is minimal. The titanium It weighs 40 per cent less and is hypoallergenic, making it ideal if you find the weight a problem, although it does show wear more easily. Regarding coatings: the PVD It is a thin layer that eventually wears away at the edges, whilst the DLC It is much harder and lasts for years. The gold plating on cheaper watches usually lasts between 2 and 5 years of daily use.

Bezel: why the diving bezel only rotates in one direction

The rotating bezel on a diving watch is unidirectional For safety reasons: it can only move anti-clockwise, so that if you bump into it by accident, it can only shorten the calculated dive time, never extend it. That of a GMT is bidirectional and features 24 markings for reading a second time zone. The tachometer A chronograph allows you to calculate your average speed over a kilometre. And on a dress watch, a slim, polished bezel is what makes the case appear smaller and more elegant than it actually is.

Straps and bracelets: the most cost-effective change

Changing the strap transforms a watch for €20–40 and is the best value-for-money upgrade there is. Measure the width between antlers (18, 20 and 22 mm are the most common) and choose according to your needs: steel for everyday use, skin for washing (never with water), rubber or FKM for sport and summer, and NATO made of nylon for a military look and quick changes. Look for pins made of quick release (quick-release) so that no tools are required. With steel bracelets, the detail that sets the good ones apart from the mediocre ones is the micro-adjustable fastening, which allows you to fine-tune the fit when your wrist swells in the heat.

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Frequently Asked Questions about Diving Watches

What does it mean for a watch to be ISO 6425-compliant?

It has passed the standardised tests for diving watches, not just the pressure test. It can be recognised by the word ‘DIVER’S’ printed on the dial next to the depth marking; without this marking, it is a water-resistant watch but not a certified diver’s watch.

How often should a mechanical watch be serviced?

Every 5–8 years under normal use, to clean and lubricate the movement and replace the gaskets. For diving watches, it is advisable to check the water resistance every 1–2 years if the watch is actually used in water.

What is power reserve and how much do I need?

These are the hours the watch keeps running without you winding it. Classic calibres last around 38–42 hours – just enough for one night; modern ones last up to 70–80 hours. If you take it off at the weekend, look for one with a power reserve of 60 hours or more: that way, you won’t have to wind it up every Monday.

Can I go for a swim in the sea whilst wearing a diving watch?

Yes: a watch rated to 20 ATM and certified to ISO 6425 is designed for just that. Rinse it with fresh water when you come out of the water, as the salt crystallises on the crown and bezel and eventually corrodes the gaskets. And always check that the crown is screwed down before going into the water.

What budget do I need for a diving watch?

It depends on how you plan to use it: there are good options in the entry-level range, as well as advanced models that are only worth the extra cost if you’re going to make the most of their features. Check the criteria in this guide, work out how you’ll actually use it, and compare the current price on Amazon before making a decision.

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