High Beat, Deep Waters: The New Defy Extreme Diver Puts Zenith Back In The Dive Watch Business

I have always felt that if you are going to call something “Defy Extreme” it should ideally defy something, and preferably in an extreme way. In the new Defy Extreme Diver, introduced by Zenith at Watches & Wonders 2024, we have exactly that, Defiance of the Extreme Dangers of the Deep – and moreover, a diver’s watch which brings high frequency precision to the party, thanks to the El Primero cal. 3620 SC. The Zenith Defy Extreme Diver has been released in a 42.5mm x 15.5mm titanium case, with either black or blue dials, and with a quick change strap system. There’s even a helium release valve, for saturation diving.

This is an interesting release for a number of reasons, not the least of which is that this is the first diver’s watch from Zenith in quite some time – around twenty years, as Brandon Baines pointed out in his article for Fratello (the last dedicated Zenith Diver was the Rainbow Elite). I was surprised to find out that it had been that long – I had, for no particularly good reason, always assumed that Zenith had one in its catalogue and for a company whose identity is so much about performance, this feels like a long overdue and very much welcome addition.

The case is heavily faceted, but not to the point that it feels antithetical to the fundamentally utilitarian mission of a diver’s watch. While it’s not strictly speaking necessary to have a large, thick case for a dive watch (the MING 18.01 is water resistant to 1,000 meters, and is just 40mm x 12.9mm) generally speaking you’re going to get larger sizes with deeper diving watches for several reasons. The first is that while there are a number of ways to engineer a water resistant case, most of them involve thicker metal and the second is that bigger generally means better legibility.

The Defy Extreme Diver comes with another feature traditionally associated with deeper diving watches – a helium escape valve, set into the case at 9:00. An HEV, it’s worth mentioning, does not enable a watch to go deeper than if it were absent. HEVs have a very specific purpose, which is to equalize pressure in the interior of a watch when a saturation diver is decompressing. Saturation divers live in pressurized chambers for the duration of their working period, which can be days or even weeks long. The chambers are usually on a surface support ship, and divers descend to working depths in a pressurized diving bell. Saturation divers can work at depths from 100 meters to up to 500 meters, and because divers don’t have to decompress between dives, they can work at depth much longer.

Decompressing can take days as well. To avoid nitrogen intoxication, divers breathe a helium and oxygen mixture and helium atoms, which are smaller than nitrogen molecules, can get into a watch case through the seals. During decompression, as ambient pressure drops, the gas built up inside the case may exert enough pressure to force the crystal off the watch; the helium release valve allows the excess gas to escape. Now, HEVs are a little controversial in consumer dive watches – recreational SCUBA diving doesn’t go any deeper than about 40 meters (the international standard for dive watches specifies 100 meters as the minimum depth rating) and you can construct a dive watch capable of withstanding saturation diving decompression that relies on case construction rather than a pressure relief valve (the one piece “monobloc” case of the original Omega Ploprof 600M is a case in point, so to speak). However, HEVs are actually useful, albeit in very specific circumstances and they’re certainly an intrinsic part of the history of technical dive watches.

You could I suppose, just unscrew the crown of your dive watch to keep pressure equalized during decompression although an unlocked crown on a dive watch is always a little hair raising. Still, this would just be during dry decompression, not actual diving, and if you have water inside your saturation diving deco chamber, you have other, much more immediate problems.

The movement, caliber 3620 SC, is related of course to the 36,000 vph El Primero, although there’s more to it than just removing the chronograph works from an EP. Zenith announced the 3620 at the beginning of 2022, in the Defy Skyline models. Zenith has its own, non-EP in house automatic Elite calibers (as well as an entire Elite collection) but the emphasis nowadays seems to be on reinforcing its identity as a maker of high frequency calibers.

The 3620 exists in two versions. The first is the 3620, used in the Skyline three hand and date models, which has a small seconds hand at 9:00 that rotates once every ten seconds, giving away its connection to the El Primero 3600 caliber, introduced in 2021 in the Chronomaster Sport chronograph. The chronograph center seconds hand in the Chronomaster Sport is driven by a gear on the escape wheel pivot (which is a daring thing to do; normally chronographs are driven by the movement fourth wheel; the escape wheel is the last in the going train and while it rotates rapidly, it generates very little torque; certainly there is not a whole lot to spare for the chronograph train). In the 3620 the escape wheel drives the ten second small seconds hand continuously, rather than a ten second, center seconds chronograph hand. The other version is the center seconds 3620 SC, which is what you’ll find in the Defy Extreme Diver models. High frequency 36,000 vph movements are pretty rare in dive watches – Grand Seiko used to make a Hi-Beat 200M diver but I think it’s out of production.

The interchangeable strap/bracelet system gives you three great options – the titanium bracelet, and two supplied straps, one rubber, and one made of recycled fishing nets. The fishing net strap has titanium end-links that allow the pass through strap to fit under the case, although I imagine you’d have a bit of an additional height penalty.

Now, we all hold dive watches to a fairly high standard in terms of functionality and rightly so. If you are going to call a watch a dive watch, there is a chance, however small, that someone is going to take it diving and an even smaller but still non-zero chance that they might need it to perform to spec. However, what we really want out of a dive watch as a daily driver rather than daily diver, is that it look the part and preferably, with a little sprezzatura thrown in there. One of the most fun aspects of the Defy Extreme Divers is the lume – three different colors, no less; the light show is reminiscent of the glow of luminescent sea creatures, far below the ocean’s surface, where no sunlight penetrates.

I’ll never not love a glow-in-the-dark bezel.

This is a great return to the dive watch business for Zenith – a technically advanced dive watch with an interesting movement, and that lume really seals the deal. The only potential gotcha I can see is the size, but 42.5mm x 15.5mm is not out of line at all for a saturation dive-capable watch, and even with the bracelet, the titanium’s going to help keep things wearable. This is I think a serious contender for any dive watch enthusiast who likes his dive watches to be high spec, and look the part.

The Zenith Defy Extreme Diver: Case, titanium, 600M water resistant, sapphire crystals front and back, with HEV. Dial, blue or black; hands, dial markers, and bezel coated with SuperLuminova X1. Movement, El Primero caliber 3620 SC, 36,000 vph/5Hz with 60 hour power reserve. Titanium bracelet plus one pass-through strap made from recycled fishing nets, and one rubber; quick change system. Price, $11,300; for more info, visit Zenith-watches.com.