Review: Rolex Sea-Dweller 1665 Double Red

At just 30 metres below the water's surface, the nitrogen that makes up 78% of our breathable air will get you high. Like laughing gas.

At 40 metres, the mellow high starts to degrade, and narcosis begins to set in. You're sleepy, disorientated.

Down to 60 metres, and now the oxygen is toxic as well. That's when the seizures begin.

At 100 metres, you're most likely dead.

In October of 1977, COMEX diver Jacques Verpeaux hit a depth of 501 metres, wearing his Rolex Sea-Dweller 1665 Double Red. This is the story of how they got there.

Watch our video review of the Rolex Sea-Dweller 1665 Double Red

The problems faced by the human body at depth are synonymous with those of a watch. Going down, the increasing weight of the water above seeks to crush any unwitting person or object that dares challenge it, while going up again, the decompression of internal gases causes dangerous expansion.

While COMEX sought to master the challenges of the human body at depth, the company left the production of the watch to the experts. Rolex was that expert. The brand had been developing water resistant watches for almost half a decade by this point, boldly demonstrating the abilities of its clamshell screw-down 'Oyster' case design with a heavily publicised journey across the English Channel on the wrist of swimmer Mercedes Gleitze. So confident was it in its product that Rolex had jewellers display operational models submerged in fish tanks for all the public to see.

Decades of research led to the Rolex Sea-Dweller

Development from there was incremental, using sturdier components to bump up the depth rating of the Oyster case to a solid 100 metres. This new design, the 1953 Submariner, catered for the increasing popularity of the compact and affordable Aqua-lung SCUBA system, and was developed for use both professionally and recreationally. If it was going to crack 500 metres, however, a lot more work was needed.

Seven years after the Submariner first hit shops and Rolex was poised to take the next big step. And it was a seriously big step. Helmed by Dan Walsh and Jacques Piccard, the submarine Trieste plunged 10,916 metres to the deepest point in the ocean, with Rolex's latest creation ... strapped to the outside.

This prototype Deep Sea Special was an experiment in what was physically possible with watchmaking, and with a crystal 33 times thicker than standard, it was most definitely built for the job. It performed flawlessly.

A thicker case and crystal added over 500m of water resistance

In 1961, one year after the Trieste visited the bottom of the ocean, COMEX was founded. Increasing demand for underwater resource drove COMEX to develop methods that allowed humans to dive deeper and deeper without the protection of a submarine. The company's experimentation with gases like hydrogen and helium neutralised the toxic reactions from breathing straight air, and the race to the deepest depths was on.

Rolex understood what was needed to beef up a watch to withstand the crushing pressure of the deep, thanks to the Deep Sea Special. Using the Submariner platform as a base, a few extra millimetres of thickness were added here and there in the caseback, crystal and bezel, and that, quite simply, was all that was needed to withstand 500 metres. The design was in fact capable of enduring more than that, and a further 110 metres were added to the depth rating later on.

A helium escape valve was developed to stop the thick crystal from popping off during decompression

But the design was not complete. While the extra strength would shrug off increasing pressure going down, it was the decompression going back up again that posed the trickiest problem. As pressures increase, inert gasses like nitrogen and helium are compressed enough to dissolve into tissue. This is not a problem until decompression occurs. Done to quickly and the gases will remain trapped in the tissue, and may lead to decompression sickness, or 'the bends', which can result in death.

So, decompression is done slowly in a diving bell to protect the divers and allow the gases to escape freely. Unfortunately, these escaping gases can escape a bit too quickly from watches, causing the crystals to pop off.

Rolex experimented with COMEX divers to develop a device that would allow gas out during decompression, but not water in during diving. Various prototype Submariners were made with this device, a sprung valve that defaulted to a shut position, but could be opened during decompression by escaping gases. Contrary to popular understanding, the valve does not open during diving. This would simply flood the watch with high-pressure water and render it useless.

The earliest models hint at the Sea-Dweller's Submariner origins

This combination of the thicker construction and the gas escape valve was given a name: Sea-Dweller. This was the watch Jacques Verpeaux would wear on his dive to 501 metres below sea level on the October of 1977.

It's easy to forget that watches of this type were the technological pinnacle of their day, forging new paths into the unknown on the wrists of some of the bravest people to ever live. These watches come from a time of exploration, of discovery, and of risk, the likes of which will likely never see again. They serve to bookmark humanity's achievements, give grounding to progress; mark a line in the sand to show just how far we've come.

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