Rolex Certified Pre-Owned: A Rolex Sea-Dweller Deepsea Ref. 116660 D-Blue

The Rolex Sea-Dweller Deepsea was originally introduced by Rolex in 2008, as the most technically advanced Rolex dive watch, and the one with the deepest water resistance. Rated to resist water pressure at depths up to 3,900 meters, the Deepsea introduced the Rolex Ring Lock system, which essentially provides a sort of inner case for the dial and movement, allowing for a less thick outer case. The principle is not unlike that found in the construction of submarines, where the outer hull, designed for hydrodynamic efficiency, encloses the inner pressure hull, which contains the engineering, living, and control spaces. In 2012, explorer and film director James Cameron dove to the bottom of the deepest point in the ocean, the Challenger Deep, in the Marianas Trench, and reached a depth of over ten thousand meters; his submersible, the Deepsea Challenger, experienced pressures of over 15,000 pounds per square inch. A specially constructed version of the Deepsea, the Deepsea Challenge, was strapped to the hull of the submersible, and withstood the same extreme pressure – the watch is rated to 12,000 meters, so there was a comfortable safety margin. In 2014, Rolex released the D-Blue version of the Deepsea, which had a gradient dial fading from a deep blue at the top of the dial, to a deep black at 6:00, which reflects the deepening darkness encountered by explorers as they descend into the abyss, and in 2018, an updated version of the reference, ref. 126660-0002, was released.

The Seadweller Deep-Sea is designed to function at depths far below those at which even modern nuclear submarines operate, and there are few submersibles capable of reaching or exceeding such depths. Cameron’s submersible had a distinctive green hull, and that color was used for the “Deepsea” logo on the dial of the watch. This is clearly a technical dive watch designed for one purpose, which is to operate in one of the most extreme environments on Earth; the outer case is 44mm x 17.8mm, which is actually significantly slimmer than would be possible without the Ring Lock system.

The Ring Lock system consists of three parts: the crystal of the watch, which is synthetic sapphire and 5.5mm thick; an inner ring, on top of which the dial sits, and which encloses the movement; and the caseback, which is in RXL titanium (a type of Grade 5 titanium). The ceramic bezel insert is fitted to the bezel itself, which is attached by a titanium clamping ring to the 904L steel case middle (the bezel is Cerachrome, and the bezel markers are filled with vapor-deposited platinum; the bezel pip inside the triangle is filled with Rolex blue-emission Chromalight, as are the white gold hands and dial markers.)

The construction of the case means that as pressure increases, the crystal and titanium caseback are pressed into the inner ring, which increases the integrity of the gaskets. The ring itself is made of an interesting material: nitrogen alloyed steel. Such steels have a higher strength to weight ratio than conventional seals and are also highly corrosion resistant, and, importantly for a watch designed to cycle between one atmosphere of pressure and 390 atmospheres, these alloys retain their strength very well with cyclic loading (that is, they show reduced metal fatigue).

This version of the Sea-Dweller has the Rolex Glidelock clasp, which offers up to 10 micro-adjustment detents of 2mm each. This is a feature which is designed to make it easier to switch back and forth between wearing the watch on a wrist, or on a wrist over the sleeve of a diving suit (and if you inclined to spend time in extreme cold, the Glidelock clasp means you can fit the watch over the sleeve of a parka as well).

One other significant feature is of course the helium escape valve, the rationale for which is a little hard to understand unless you understand how saturation diving works. Saturation divers breath a special gas mixture in which the nitrogen found in the Earth’s atmosphere is replaced with helium; the reason for this is that as pressure increases, nitrogen gas dissolves into the bloodstream and above a certain concentration can cause nitrogen narcosis. Helium doesn’t have this effect when you breathe it under pressure. However, helium atoms are small enough to work their way into the case of a watch and over prolonged periods, enough helium builds up inside the case to exert considerable outward pressure. The reason this happens is because in between working dives, saturation divers live inside sealed habitats on the decks of support ships (the divers go to and from the actual dive site in pressurized diving bells) so that they don’t have to waste time decompressing between each dive. At the end of a shift, which can be up to several weeks long, the divers decompress inside the surface habitat but as pressure inside the habitat drops, the helium built up inside the watch case can push outward hard enough to pop the crystal off the watch.

The Deepsea Sea-Dweller is a watch made for a singular purpose (with elements of its design echoing the adventures of a singular explorer) and it’s a watch ideal for anyone who understands that it’s engineered to function in a particular environment and under specific conditions. As much a triumph of engineering as watchmaking, the Deepsea is one of those rare watches in which almost pure functionality has resulted, paradoxically, in an aesthetic all its own.

See the Rolex Deepsea Sea-Dweller ref. 126660-0002 here, and view our Rolex Certified Pre-Owned Collection.