At the beginning of the 20th century, the pocket watch was the most common and practical way for people to tell the time.
Hans Wilsdorf, who began his career in 1900 working for a watch company in La Chaux-de-Fonds, observed how lifestyles were changing and particularly the rise in popularity of sports and outdoor pursuits. The man who was to found Rolex a few years later realized that pocket watches, which had to be protected within the folds of clothing, were not suited to these new kinds of use. An enterprising man of vision, he decided he would create watches to be worn on the wrist that their owners could count on for reliability and accuracy in their modern, active lives.
We must find a way to create a waterproof wristwatch.
Hans Wilsdorf, 1914
One of the main challenges facing Hans Wilsdorf was to find a way to protect the watches from dust and moisture, which can cause clogging or oxidization if they find their way inside the case. In a letter in 1914, he spoke of his intentions to Aegler, the firm in Bienne which would later become the Manufacture des Montres Rolex S.A.: “We must find a way to create a waterproof wristwatch.”
In 1922, Rolex launched the Submarine – a watch attached on a hinge inside a second, outer case, whose bezel and crystal screwed down to make the outer case watertight. Accessing the crown – to wind the watch or set the time – required opening the outer case. The Submarine marked the first step in Hans Wilsdorf’s efforts to create a completely sealed watch case that was convenient to use.
The Oyster case, the fruit of these efforts, was patented four years later in 1926. A system of screwing down the bezel, case back and winding crown against the middle case ensured that the case was hermetically sealed and protected the inside of the watch from harmful elements on the outside. Hans Wilsdorf chose to call the watch – as well as its case – the “Oyster” because of the fact that “like an oyster, it can remain an unlimited time underwater without detriment to its parts.” This invention marked a major breakthrough in the history of watchmaking.
To promote the exceptional qualities of his Oyster watch, the following year Hans Wilsdorf decided to do something innovative. Learning that Mercedes Gleitze, a young secretary from Brighton, England, was preparing to swim across the English Channel and, if successful, would become the first British woman ever to achieve this feat, he asked her to carry an Oyster with her to demonstrate that the watch was completely waterproof. After Gleitze’s gruelling swim in the bitterly cold waters, a journalist for The Times newspaper reported that she “carried a small gold watch, which was found [...] to have kept good time throughout.”
The Oyster was the World's first waterproof wristwatch thanks to its hermetic Oyster case.
The Oyster case, a revolutionary design
The perfectly hermetic Oyster case is emblematic of Rolex watches. Patented in 1926, it is composed of a bezel, case back and winding crown that screw down against the middle case. These components have undergone changes over time to further reinforce the watch’s waterproofness and to meet the needs of divers as diving materials and techniques developed, allowing them to descend to ever greater depths.
The bezel on the original Oyster case was fluted, allowing it to be screwed down onto the middle case using a tool exclusive to Rolex. In following years, the architecture of the Oyster case evolved to become more robust and reliable. The technical changes brought to the case also made it possible for a rotatable bezel to be fitted, on divers’ watches in particular.
The crown on the original Oyster case screwed down onto the middle case. In 1953, Rolex introduced the Twinlock winding crown, which incorporated a patented system with a double seal. The principle was taken a step further in 1970: the Triplock winding crown, comprising an additional sealed zone, reinforced the waterproofness of the watches on which it was fitted – among them its models designed for diving.
The back of the Oyster case was edged with fine fluting – as it still is today – enabling it to be screwed down hermetically against the middle case. On the current divers’ watches, depending on the model or version, the case back is made of Oystersteel or 18 kt gold.
Just below the surface
Just as changing lifestyles prompted Rolex to invent a waterproof case, the brand next turned its attention to the design and development of wristwatches that met the needs of the new deep-sea diving professionals. In 1953, the Submariner was created: the first divers’ wristwatch guaranteed waterproof to a depth of 100 metres (330 feet). Its rotatable bezel with a graduated insert allowed divers to monitor their time underwater, helping them manage their breathing gas reserves. The security of the Oyster case was enhanced thanks to a new screw-down winding crown with the Twinlock system, benefitting from two sealed zones.
In 1970, the principle was further developed with the introduction of a third sealed zone, and the Triplock winding crown was born. The hands and hour markers were coated with a luminescent material, enabling divers to read the time in the dark conditions underwater. Rolex went on to make further technical advances that rendered the Submariner waterproof to a depth of 200 metres (660 feet) in 1954, and 300 metres (1,000 feet) in 1989. The version with date, introduced in 1969, would be waterproof to a depth of 300 metres (1,000 feet) by 1979.
Rolex was one of the first brands to accompany exceptional individuals in their ventures and explorations. Aware of the mutual benefit to both parties and seeing the world as a living laboratory, Hans Wilsdorf equipped them on their expeditions with Oyster watches. To test the reliability of its timepieces, Rolex asked professional divers to wear them on their missions, afterwards gathering impressions and suggestions for ergonomic or technical improvements. This procedure became an integral part of the Rolex development process.
Among the people Rolex worked with to test the Submariner was French underwater photographer, engineer and explorer Dimitri Rebikoff. In testing the watch, over five months Rebikoff carried out 132 dives, which took him to depths of between 12 and 60 metres. His report was very positive: “We are able to confirm that this watch has not only given entire satisfaction in diving conditions which were extremely tough and particularly dangerous for the material used, but that it has proved an indispensable accessory for all diving with independent equipment.”
A glimpse of the deep
Certain sub-aquatic scientific projects and expeditions also presented ideal opportunities for Rolex to test its watches in real-life conditions. In 1960, the brand teamed up with one such project, an expedition led by Swiss oceanographer Jacques Piccard and U.S. Navy Lieutenant Don Walsh. On 23 January, on board the bathyscaphe Trieste – designed by Jacques’ father, Auguste Piccard, a Swiss physicist and explorer with whom Rolex had worked since the early 1950s – Piccard and Walsh achieved a feat by descending to the deepest part of the world’s oceans, the Mariana Trench in the Pacific Ocean.
Affixed to the outside of the submersible was an experimental Rolex watch called the Deep Sea Special, which accompanied the two men to the extreme depth of 10,916 metres (35,814 feet). The domed crystal on this prototype was designed to withstand the enormous pressure exerted at such a depth. When the Trieste resurfaced after some eight and a half hours under the sea, the watch was found to have kept perfect time, which validated the technical choices made by the brand during its design. It would be decades before any such expedition would be repeated.
The watch for the sea dwellers
During the 1960s, techniques were developed that made extended dives possible at ever greater depths. One of these new methods, designed for divers working on undersea infrastructures, for example, was “saturation” diving. A special mix of breathing gases with a high helium content makes it possible for divers to stay under the sea for periods of several days or even weeks, and avoid the toxic effects on the human body of pressure at great depths. It also involves keeping the divers in an environment with a pressure equivalent to that of the water at their working depth.
To do this, the divers stay for several days or weeks at a time in a pressurized habitat – a hyperbaric chamber – which they leave only to carry out their dives. It also means that they need only undergo a single decompression process at the very end of the mission. Depending on the time spent underwater and the working depth, decompression can take anywhere up to several days.
In the hyperbaric chambers, the watches worn by the divers gradually fill with helium, a gas with atoms so tiny they can penetrate the waterproof seals. During decompression, this helium remains trapped in the watch case with the attendant risk of creating a pressure differential in relation to the chamber. The gas in the watch case is unable to escape as quickly as the external pressure is dropping, which can damage the watch or force the crystal out of the case. In 1967, Rolex patented the helium escape valve, a safety release valve that activates automatically when the pressure inside the case is too high, allowing the surplus gas to escape.
That same year, Rolex launched the Sea-Dweller, a divers’ watch guaranteed waterproof to 610 metres (2,000 feet), and to 1,220 metres (4,000 feet) in 1978. Equipped with a helium escape valve, it was the ideal tool for saturation divers, the explorers and pioneers of the deep sea. As a natural progression, the brand partnered with the underwater habitat project Tektite in 1969 for which four aquanauts spent 58 days below the surface. They were equipped with Rolex watches. The following year as part of Tektite II, Sylvia Earle led an all-female mission. The marine biologist – a Rolex Testimonee since 1982 and National Geographic Society Explorer-in-Residence from 1999 – wore a Rolex watch during the two weeks spent working in a sub-aquatic habitat.
In 1967, Rolex began a partnership with HYCO (International Hydrodynamics Company), a Canadian firm specializing in the development of submarines. Rolex Sea-Dweller watches were attached to the outside of HYCO submersibles on various missions. After one dive of around four hours at a depth of 411 metres (1,350 feet), HYCO sent Rolex its conclusions regarding the Sea-Dweller’s performance: “During all the phases of testing the watch performed beautifully.”
During all the phases of testing the watch performed beautifully.
HYCO, 1967
In 1971, Rolex formalized its partnership with Comex (Compagnie Maritime d’Expertises). This French marine-engineering firm based in Marseilles agreed to equip its divers with Rolex watches and report back regularly on the watches’ performance so the brand could further enhance their reliability and functionality. In parallel to its offshore interventions, Comex also conducted tests in view of developing new technologies to assist its operations.
Among these were hyperbaric chambers that reproduced the pressure exerted at depth and posed great difficulties for divers and equipment. In 1988, Comex organized the Hydra VIII expedition, during which six saturation divers descended to 534 metres (1,752 feet), setting a world depth record for open-sea diving that still stands today. All were equipped with Sea-Dweller watches. A few years later, in 1992, for the Hydra X experiment, a Comex diver reached a simulated depth of 701 metres (2,300 feet) in a hyperbaric chamber. For the 43 days of his mission he was wearing a Sea-Dweller watch.
The Deepest Depths
Rolex continues to defy underwater pressure by never ceasing to perfect its watches. In 2008, the brand presented the Rolex Deepsea, whose patented case architecture – the Ringlock system – enables it to withstand the pressure at a depth of 3,900 metres (12,800 feet). The system comprises a slightly domed sapphire crystal, a nitrogen-alloyed steel compression ring and a case back made from a titanium alloy. The unidirectional rotatable bezel of the Rolex Deepsea is fitted with a 60-minute graduated black Cerachrom insert that allows divers to safely monitor their immersion time.
The properties of this high-tech ceramic produce an insert that is exceptionally strong, virtually scratchproof, and whose colour, unaffected by ultraviolet rays, remains stable over time. This watch for the extreme depths is also equipped with another exclusive invention that enhances its legibility: the Chromalight display. An innovative luminescent material emitting a blue glow is applied to the hands, hour markers and the capsule on the bezel. The luminosity duration is almost double that of a standard phosphorescent material, and the intensity of the glow is more consistent over the emission time.
In accordance with the standard for this type of watch, all Rolex divers’ watches are tested at their guaranteed waterproofness depth plus an additional 25 per cent. This effectively means that in the laboratory, within a hyperbaric tank developed jointly by Rolex and Comex, the Rolex Deepsea (which is guaranteed waterproof to 3,900 metres) is subjected to the pressure exerted at 4,875 metres deep.
The Rolex Deepsea was the inspiration behind the Rolex Deepsea Challenge, the experimental divers’ watch that, on 26 March 2012, attached to a manipulator arm of the submersible piloted by explorer and filmmaker James Cameron, descended to the place last visited by Jacques Piccard and Don Walsh in 1960: the Mariana Trench. Guaranteed waterproof to the extreme depth of 12,000 metres (39,370 feet), the watch included all of the brand’s technical innovations in terms of waterproofness, and, in the test phases, successfully withstood the pressure exerted at 15,000 metres. At this depth, the Ringlock system’s central ring is subjected to a pressure equivalent to a weight of 20 tonnes.
