Rolex designed the Sea-Dweller specifically for professional divers with the Compagnie Maritime d'Expertise or COMEX. At the time, the divers at COMEX were already using watches by Rolex, specifically the . Unfortunately, the Submariner Reference 5513 encountered problems when exposed to the extreme depths at which the COMEX divers worked. Simply put, COMEX employed a new diving technique, called saturation diving, in which the divers used a mix of hydrogen, helium and oxygen rather than the standard nitrogen and oxygen. When not working, the divers would rest in a pressurized chamber, breathing helium-infused air and allowing the built-up helium to leave their bodies.
Since saturation diving decreases a diver's decompression interval, the helium molecules left their bodies faster than they left their watches, causing a build-up of pressure that would blow the crystals off their watches. COMEX approached Rolex with this problem, and Rolex presented a solution: install a titanium Helium Escape Valve on the case at 9 o'clock, which would allow the helium molecules to escape the watch faster. A waterproof O-Ring secured a spring-loaded piston to the outside of the case, which pressed against the O-Ring when the watch was exposed to increased water pressure. Rolex gave COMEX a few of these special prototype 5513 Submariners with Helium Escape Valves, and the problem was solved. Later, in 1967, when COMEX requested a hundred more, Rolex issued a new Reference number, 5514, and placed the COMEX logo on the dial.
These Reference 5514 Submariners proved such a success that Rolex decided to release them to the public in a brand-new Reference: 1665, the Sea-Dweller. This first Reference of Sea-Dweller was equipped with the Calibre 1575 movement and a thicker crystal, enabling the public to buy a watch capable of descending to the punishing depth of 2000 feet (or 610 meters) at which the COMEX professionals worked.
In 1978, the Reference 1665 Sea-Dweller was replaced by the Reference 16600, which was fitted with the Rolex Caliber 3035 movement. Now fitted with a synthetic sapphire crystal, the Reference 16600 boasted an even greater depth rating: an impressive 4000 feet (or 1220 meters). This was possible, in part, due to a larger Helium Escape Valve.
The Reference 16600 ran until 2008, when it was replaced by the current model, the gargantuan 44mm Reference 116600. Rugged and dependable, the Reference 16600 is the last 'Dweller with classic Oyster dimensions. A quintessential tool watch with a solid construction, this example comes fitted with its original heavy duty Oyster bracelet with solid end links (SEL) and has just taken a turn through our shop. It's a perfect example of a precision instrument that can take a beating (and a bath!) and still run, and is a lesser-seen alternative to the omnipresent Submariner. A contemporary classic, for sure.
