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A New Type of Dive Watch: The Rolex Sea-Dweller, Reference 1665

May 19, 2016

BY Paul Altieri


As the company that invented the world’s first waterproof watch, Rolex has always been a leader in building watches that can survive in aquatic conditions. However, in the late 1960’s, deep-sea experiments called for a different kind of watch – one that could withstand the extreme pressures of saturation diving. From this initial need, Rolex reinvented the dive watch and created the first Sea-Dweller.

Crown Vintge SeaDweller 1665

See the details on the crown of a vintage Sea-Dweller 1665.

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The French deep-sea diving company, Comex was among the first to experiment with saturation diving – a method of diving, in which helium replaces nitrogen in the air, allowing divers to work at much greater depths. The numerous hours spent in pressurized chambers would force helium molecules inside the divers’ watches, causing the crystals to rupture during decompression.

The solution to Rolex’s pressurization problem came in the form of a helium gas escape valve on the Sea-Dweller. These valves allowed trapped helium molecules to exit freely, without generating pressure inside the watch. The first ever helium escape valves appeared on standard reference 5513 Submariners that were made specifically for Comex. These Submariners received 5514 reference numbers, and were never released to the public.


Comex was among the first to experiment with saturation diving.

Experimentation with these modified Submariners led Rolex to create the Sea-Dweller, tripling their previous depth rating. The first ever Rolex Sea-Dwellers were modified Submariners, and they did not feature helium gas escape valves. It is believed that 30 such watches were created, although few remain as most failed during saturation dive testing.

Sea-Dweller 1665

The Stainless Steel Sea-Dweller 1665 is still an impressive watch.

Sea-Dweller 1665

Two different versions of the reference 1665 Sea-Dweller were released. Early examples used cases that were thinner, like those found on Comex Submariners, while later examples of the reference 1665 used thicker cases that Rolex made exclusively for their Sea-Dweller line of watches.

double-red sea dweller

Early examples used cases that were thinner, like those found on Comex Submariners.

Roughly 100 of the first reference 1665 Sea-Dwellers were made, and they are unique from all others in that they have ‘patent pending’ engraved on the case back. At the time of their release, Rolex had filed for, but had not yet received the patent for the helium escape valve. Such examples are the very first Sea-Dwellers, and they are highly collectable today.

The later reference 1665’s were Rolex’s first regular production run of Sea-Dwellers. They were based upon the thicker case design, and featured a domed crystal and the newly patented, helium escape valve. These reference 1665 Sea-Dwellers have two lines of red writing on the dial, earning them the nickname, “Double Red Sea-Dwellers” among collectors.

Sea-Dweller 1665

The two lines of red on this Sea-Dweller make it a rare and collectable watch.

The reference 1665 Sea-Dweller is significant to Rolex’s history because it represents their ongoing pledge to produce high-quality timepieces that excel in extreme conditions. As soon as advances in diving technology created the need for a new kind of dive watch, Rolex was there to fill that need with a watch that surpassed every necessary specification.





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