Who dives to 3,900 metres? The answer shouldn’t be long in coming, as no ordinary human being, however much in search of extreme underwater sensations, can hope to come anywhere near such abysmal depths. There is, however, nothing ordinary about the divers at Comex (Compagnie Maritime d’Expertise), a French company and world leader in sub-sea engineering, operations and technologies. They are the ones Rolex commissioned to fine-tune specifications for its new Oyster Perpetual Sea-Dweller Deepsea. This wasn’t the first time the Geneva firm has called on Comex’s expert divers, who already contributed their skills to develop the Submariner and help launch the first Sea-Dweller models.
Now Rolex is back with a model that pushes back the boundaries of past performances. “The technological innovations behind this watch were devised to meet the requirements of extreme professional diving,” commented Stéphane Dufour and Eric Grippo at the Société Suisse de Chronométrie’s most recent study day. “Clear objectives were set out. These were to strike the right balance between the size of the watch and the water-resistance such depths imply, and to ensure comfort of use in terms of legibility and adjusting the fit.”
A patented system
The colossal pressure exerted at 3,900 metres underwater is more than the traditional architecture of Oyster-type cases was designed to withstand. Rolex’s response was to develop an entirely new solution in the form of the patented Ringlock System. It revolves around three separate elements: a sapphire crystal, a steel ring and a titanium case back. “The steel ring is set between the crystal and the case back to absorb pressure from them,” explains Stéphane Dufour. “This is possible thanks to a nitrogen-alloyed stainless steel with an elastic limit twice that of 904L steel. The titanium case back was optimally designed using digital simulation techniques, as were the thickness and domed shape of the sapphire crystal. The end result is a case that is less than 18mm high.” Note that the helium escape valve, on the caseband at 9 o’clock, is in the same high-performance steel as the Ringlock System ring.
Equal consideration went into the bracelet design. The safety catch combines with the rack-system Glidelock clasp and the three-part Fliplock folding extension links. The two systems together allow the length of the bracelet to be adjusted by up to 36mm in very fine increments, as a result of which the Sea-Dweller Deepsea can be worn over any type of diving suit.
In yet another innovation, the ceramic unidirectional bezel rotates thanks to 120 Breguet teeth and a spring-mounted system in the case middle. This prevents accidental clockwise rotation and produces a sound when the bezel is rotated anti-clockwise. Three spring-mounted ball-bearings control rotational torque. The final problem to resolve was legibility. Rolex has done this by using Chromalight, a new luminescent substance inside a capsule that gives a blue glow to the zero marker on the graduated bezel, and to the markers and hands on the dial. Calculations have shown a 308% improvement in performance after 180 minutes in the dark, compared with the substance used on previous Sea-Dweller models.
The Sea-Dweller Deepsea watch is fitted with the COSC-certified 3135 calibre, a self-winding movement with a 48-hour power reserve, for precision chronometry. It features a Parachrom balance-spring with high resistance to shocks and magnetic fields. Rolex already achieved the impossible in 1960 when an experimental prototype, the Deepsea Special, was attached to Jacques Piccard’s Trieste bathyscaphe and sent 10,916 metres down into the Mariannes Trench. Today, the Sea-Dweller Deepsea confirms the brand’s unique status in the deepest underwater world.