Dive watch guide: ISO 6425, water resistance and the models worth buying

The dive watch is the most copied shape in watchmaking, and for good reason: a legible dial, a bezel you can grip with wet fingers and a case that survives salt water make it the most useful everyday watch there is. Most divers are never worn below a swimming pool. That is fine. It still helps to know what separates a real diver from a watch that only looks like one.

What ISO 6425 requires

ISO 6425 is the international standard for divers' watches. A watch that meets it has at least 100 m of water resistance, a way to measure elapsed dive time protected against accidental turning (usually a unidirectional bezel with minute markings), and a dial and hands that stay readable in the dark. Test samples are also pressure, shock and magnetism tested. Not every brand certifies its divers to the standard, but the good ones are designed to the same rules.

How much water resistance do you need?

• 100 m: swimming and snorkelling. The minimum for a dive watch under ISO 6425.
• 200 m: recreational scuba and the practical sweet spot. Most modern divers sit here.
• 300 m and more: for professional diving and for peace of mind. Look for a screw-down crown and a helium valve on the deepest models.

Tudor Black Bay

Tudor launched the Black Bay in 2012 and it quickly became one of the most wanted divers under €5,000. The design borrows from Tudor's historic divers: domed crystal, large crown and a bezel with a clean minute scale. See all Tudor watches in stock.

Longines HydroConquest and Legend Diver

Longines offers two very different divers. The HydroConquest is the modern sports watch, with a ceramic bezel and 300 m water resistance on current models. The Legend Diver reissues the brand's 1960s compressor diver with an inner rotating bezel set by a second crown. Browse Longines.

TAG Heuer Aquaracer and Oris Aquis

The Aquaracer Professional 200 and 300 are TAG Heuer's tool divers, with a faceted bezel that is easy to grip. Oris builds the Aquis as a pure dive tool with an integrated rubber or steel bracelet, and the Divers Date as a vintage-styled alternative. See TAG Heuer and Oris.

Seiko Prospex and Tissot Seastar: divers under €1,100

Seiko has made dive watches since 1965 and the Prospex line carries that history: the Turtle, the Samurai and the Sumo are nicknames collectors use for its classic cases. Solar Prospex models charge from light and never need a battery change in normal use. Tissot's Seastar 2000 Professional pairs 600 m water resistance with the Powermatic 80 movement. Compare prices in the dive watch category.