Hands-on Review: Rolex Sea-Dweller Ref. 126600

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Everybody knows the Rolex Sea-Dweller. Well, anyone reading this site anyway. It is perhaps the most illustrious of all diving watches. The earliest Sea-Dwellers were Ref. 1665. The early prototypes were known as Single Red Sea-Dwellers. Some had gas escape systems, some did not. And in 1971, Rolex made a commercially available series of the Ref. 1665 incorporating the gas escape system. These were the famous Double Red Sea-Dwellers. A few iterations of Sea-Dwellers followed through the long course of its history and today, we review the latest in this line of professional diver watches – the Rolex Sea-Dweller Ref. 126600.


Rolex Sea-Dweller Ref.12660

The Rolex Sea-Dweller Ref. 126600 with red text typically referred to as Single Red. The 2017 edition is the first time the Sea-Dweller incorporates the Rolex cyclops, a lens to magnify the date.


Some historical aspects

In November of 1967, Rolex received a patent for a helium escape valve (HEV). The patent was a solution installed in some prototype Sea-Dweller Ref. 1665, the so-called Single Red Sea-Dweller or the Mark 00. These watches were special issues and the Ref. 1665 were not commercially available until the launch the Sea-Dweller Ref. 1665 in 1971. The commercial Sea-Dweller were also known as the Double Red Sea-Dweller for their distinctive dial markings, and all were equipped with a HEV.

This patent  (Swiss patent no 492,246) was shared with Doxa Watches who released their Doxa SUB 300T Conquistador in 1969 with a HEV, handily beating Rolex for a commercial offering of a watch with a HEV by two years.

However, the roots of the first Sea-Dwellers are traced to 1967, thus marking the 50th Anniversary this year in 2017. According to Rolex guru, Eric Ku of Ten Past Ten, These were made with feedback from the US Navy and other governmental agencies and commercial diving outfits.

“The story is that Bob Barth (Navy Diver) and member of the Sealab (Experimental Diving Habitats) had problems when decompressing and the crystals off his submariner would pop off. He relayed this info to T. Walker Lloyd”, said Eric in a chat message we had with him.  Walker was a dive buddy of Bob. Bob made an analysis and suggested a solution in the form of a helium escape valve.” Walker then summarised these ideas and relayed them to Rolex. “And they (Rolex) started testing a new dive watch with greater water resistance. The very first version of these watches was the Single Red Sea-Dweller, with a depth rating of 500m. These watches were given for test to US Navy divers and used on missions like Tektite 1, 2. They were also given to other commercial divers with companies like General Electric, Westinghouse etc…”

T. Walker Lloyd was later hired by Rolex as Oceanographic Consultant.

According to Antiquorum, only six of these prototype Ref. 1665 Single Red Sea-Dwellers were ever made. All bear the markings in a single line of red text “SEA-DWELLER”. The depth rating is in white and marked as 500 m/1,650 ft. Out of the six, only two had HEV, making the rest essentially Submariners with greater water resistance. One of these with the HEV was sold in a Antiquorum Lot 126 of their auction in Geneva on 11th November 2012. It achieved a price of CHF 490,900 including premium. The sale documentation showed that case No. 1602931, Ref. 1665 was made in 1967.



ROLEX REF 1665 – THE SINGLE RED PROTOTYPE – PATENT PENDING – 500M-1650FT – ONE OF SIX KNOWN Rolex – Ref. 1665 – Single Red Sea-Dweller – Patent Pending, Rolex, “Oyster Perpetual Date, Sea-Dweller, Submariner 1650 ft. = 500 m., Superlative Chronometer, Officially Certified,” case No. 1602931, Ref. 1665. Made in 1967. Fine and extremely rare rare, center seconds, self-winding, water-resistant, stainless steel diver’s chronometer wristwatch with double red Sea-Dweller logo, helium escape valve, date and a stainless steel riveted Rolex Oyster Ref. 7206 bracelet with patent pending extension link.
Text and pic by Antiquorum.


Another Single Red Sea-Dweller Ref. 1665 Mark 00 was sold by Sotheby’s at as Lot 216 in the June 2013 New York Auction. Case number 1602928 was recorded as made in 1967, and it had no HEV. Sale price was US$383,000 including premium.

Though Antiquorum notes in their Auction Catalog that only 6 Single Red Sea-Dwellers were made, we have reason to believe this is incorrect. In a report in Perezcope published in August 12, 2017, 12 such Single Red Sea-Dwellers were recorded by the author Jose Pereztroika. Jose shows pictures and details for 11 of those. Click here for the full details. Interestingly, out of the 12, 5 had HEV.

An example of the early Ref. 1665 without HEV is found in a report by Monochrome here.

We do note that Single Red Sea-Dwellers are not limited to the first prototypes made in the 1967 era, but Rolex continued to make some till the late 1970s. One example is made in 1975 and was sold as Lot 203 in Antiquorum‘s New York auction of June 22nd, 2017. It achieved a US$ 31,250 with premium.

In earlier reports (Dowling & Hess, The Best of Time: Rolex Wristwatches : An Unauthorized History), the Rolex Ref. 5513/4 with HEV was quoted as the origins of the Sea-Dwellers. These were issued to Comex divers. We now understand this was only from about 1971 when the close relationship between Rolex and Comex began. And is verified as such by the earliest examples of these watches date from there.

The early Sea-Dwellers from 1971 which were commercially available were marked with a red text “SEA-DWELLER” and a second line also in red “SUBMARINER 2000”. The words “Patent Pending” are engraved on the case back. These are known to collectors as Double Red Mark 1 watches (though some Mark 2 watches were also engraved “Patent Pending”) and have serial numbers from 1.7 million to about 2.2 million. These are highly desirable in the secondary market, fetching high prices, though not quite as astronomical as the prototype Single Red Sea-Dwellers. Some believe only 50 of these Double Red Mark 1 Sea-Dwellers were made, but other experts think the number may be as high as 200.



The Rolex Sea-Dweller Ref. 1665 Double Red Mk1. The black dial can fade, an effect known by Rolex aficionados as a tropical dial. This example has an unfaded dial. Photo credit: Double Red Sea Dweller www.drsd.com.


Rolex continued to make the Double Red until 1977. Later editions after serial number 2.2 million are called Mark 2. A total of 4 dial variations were offered during those years.



The illustrated history of the Rolex Sea-Dweller and appoximate dates. For a full sized image click here.
Pic from https://perezcope.com/


Why Helium Escape Valve?

So what is the HEV, and why is it essential? We go back to its historical roots. The time was the early 1960s, where oil exploration was at its full swing. And the explorations called for work to be done in deeper and deeper seas.

The first hurdle to overcome is to find a way where divers can work in these depths (we are talking greater than 200m here) for periods of time longer than 2-3 hours. Any shorter period was not useful for any work which was complex. When a diver ascends from the deep water too quickly, the sudden reduction of pressure releases the nitrogen compressed in the air he breathes and forces it to bubble out in his blood. This is a condition known as the Decompression Sickness, or the bends. This was solved by switching the diver’s air from a natural mixture of oxygen and nitrogen to one with oxygen and helium. The divers are still required to spend time in a decompression chamber, but for periods less than if they breathed a normal O2/N2 mixture.

Secondly, to save even more time, instead of having to decompress after every dive, divers would live in a dry pressurized chamber on or connected to the diving support vessel, oil platform or other floating work station at approximately the same pressure as the work depth. The Sealab and Tektite were the experimental stages where this concept was tested. This chamber, shown in the schematic below is usually also at about the same depth as the working area.


Saturation system schematic plan

Schematic plan of a simple saturation system showing the main pressure vessels for human occupation DDC – Living chamber DTC – Transfer chamber PTC – Personnel transfer chamber (bell) RC – Recompression chamber SL – Supply lock.
Source: Wikipedia.


The divers would enter the decompression chamber and live in it for the entire tour of duty which may be several weeks. At the beginning, the chamber is lowered to operating depth, and air in the chamber would be gradually changed to the oxygen-helium mix and the air pressure would be increased to match that on the dive depth. This is a gradual change, and might take a few days to complete. When complete, the diver can then stay in the pressurised living chamber, be transported to his work place in the pressurised bell, returning only to the chamber after each shift. After his tour of duty, which may last up to weeks, the conditions in the chamber would gradually be reversed, and eventually become a normal gas mixture at a atmospheric pressure.

This system is known as saturation diving. Saturation refers to the fact that the diver’s tissues have absorbed the maximum partial pressure of gas possible for that depth. Once the tissues become saturated, the decompression time will not increase with further exposure. And this system makes it safer for the divers, reduces decompression sickness, as well as allowing the divers to spend more time at work to handle complex tasks.

Under such conditions, even the regular Rolex Submariner was fully capable of working at the depths the divers did. Perhaps due to the superior construction of the case, the Submariner is waterproof and air tight, and over short dives, the pressure inside the case is maintained at sea level. But over the periods of long high pressure dives and of living in the high pressure oxygen-helium chamber, the smaller molecules of helium permeate the crystal of the watch, and increase the pressure inside the case to equalise with the surroundings.

All is good as long as the environment stays high pressure. But when the chamber is decompressed at the end of the duty cycle, the high pressure helium within the case is not able to escape fast enough to equalise the pressure within and outside. This internal pressure would just blow up the crystal out of the watch.

“Bob Barth and the rest of the Aquanauts were killing time reading and playing table games. Suddenly, they heard a loud popping sound and something hit the ceiling of the pressure chamber and bounced back to the table. The men looked at each other and were puzzled. The object that landed on the table was a Rolex 5512 crystal.”

The solution found by Bob was to incorporate a one-way valve to allow the helium to escape. It was implemented by Rolex in the prototype Single Red Sea-Dweller Ref. 1665. It is quite a simple solution where a valve is equipped with a spring to keep it closed. When the pressure within is too high, the valve is activated, releasing the trapped helium and lowering the pressure within. This valve releases the pressure automatically as the spring holds it closed until the pressure difference is large enough to activate it. Rolex and Doxa use this type of HEV. A manual system used in most Omega Seamasters (except the Ploprof which uses an automatic HEV. Ploprof review coming soon!) is where a screwed down crown is manually open to allow this to happen.

Another solution, as we saw in our Grand Seiko Hi-Beat Professional Diver, was to make the case ultra strong, with a special gasket. As far as we know, the Seiko solution is unique to them.

Hands-on Review: Rolex Sea-Dweller Ref. 126600

We covered the basics in the Press Release published in our Baselworld 2017 coverage.

From even as earlier, Rolex’s pioneering involvement in deep sea work are quite well known. See our two part article on the Deep Sea Special and the Deep Sea Challenge. Part 1 is here, and Part 2 is here.


Rolex Sea-Dweller Ref. 12660.

The Rolex Sea-Dweller Ref. 126600, now in 43mm case, with a ceramic bezel and a cyclops over the date.


The case, dial and hands

The new Rolex Sea-Dweller Ref. 126600 was introduced in Baselworld 2017, and only recently (early August 2017) did stocks arrive to the Singapore market. The demand for the Ref. 126600 as well as the recently discontinued Ref. 116600 is very high. We understand that a waiting time of up to 3 to 5 months or more is indicated for the former.


Rolex Sea-Dweller Ref. 12660.

The Ref, 16600 on the left belonging to the author (circa 2008) and the new Ref. 126600 on the right.


The Rolex Sea-Dweller Ref. 126600 carries over the handsome good looks of its predecessor. The case is enlarged over the Sea-Dweller Ref. 116600 which was released in 2014. The Ref. 116600 is also very similar to the Ref. 16600 which was discontinued in 2008. The main difference between the Ref. 116600 and the Ref. 16600 is that the Ref. 116600 featured a Cerachrom (Rolex-speak for its version of ceramic) bezel and a new bracelet with solid links. There are a few other differences, but these are relatively minor. Both cases are 40mm in diameter. The 116600 will now be discontinued for the new Ref. 126600, which features the following changes to the case and dial:

  1. The case size enlarged to 43mm.
  2. A cyclops now sits over the date at 3 o’clock to provide magnification to the date. This was previously not possible, but Rolex say that they are finally satisfied with a new adhesive used to ensure that the cyclops does not pop out during operations in the deep. Some may argue that a date is superfluous in a diving watch, but we note that Rolex designed the Sea-Dweller for saturation diving, where the divers remain at the depth for days or weeks. It is thus critical for them to know what the date is in an environment where they are not able to see sunrise and sunset.
  3. The dial now has a gloss finish instead of the matte finish.
  4. The most obvious feature is the text for “SEA-DWELLER” is now in red instead of white. This is perhaps a significant nod towards the Single Red Sea-Dweller Ref. 1665, and an indicator to mark the 50th Anniversary.


Rolex Sea-Dweller Ref. 12660.

The cyclops makes its first appearance on the Rolex Sea Dweller. Now in a larger case, but the same 1200m depth rating.


The 18k white gold appliqué markers are large and clearly legible, and filled with Chromalight, a Rolex Superluminova variant which emits a light blue lume in the dark and lasts longer with more even lume than the common C7 Superluminova. The hour hands are javelin style, and the hour hand are what is commonly known as Mercedes hands, are also in-filled with Chromalight. The seconds hand carries a lollipop with a Chromalight filling and counterbalanced by another lollipop on the other end. The hands are in 18k white gold.

The black Cerachrom bezel remains, though now larger to sit nicely over the larger case. Cerachrom is a kind of ceramic which is scratch-proof and resistant to colour change caused by ultraviolet rays. The bezel is uni-directional, and moves in 120 discrete and rather satisfying clicks to make one revolution.


Rolex Sea-Dweller Ref. 12660.

The Cerachrom bezel features the 120 click uni-directional rotation. Both the bezel and crown feature deep scoring to ensure good grip with gloved hands.


Depth rating remains at 4000ft – 1220m, and a Triplock crown is used. as indicated by the three dots below the crown logo.

Finishing on the case, dial and hands are very well done, and remain a reference standard for the industry. The entire built quality is first grade, if not at haute horologie levels. certainly at the top of the engineering finish at industrial levels. It feels solid, dependable and reliable. Qualities highly desirable in a professional diving watch, where one’s life might depend on the watch working perfectly.


The movement

As usual in a Rolex, the case back is in stainless steel (Rolex uses 904L) and solid. The movement is the new caliber 3235, which is certified to the Rolex Superlative Chronometer certification (COSC plus Rolex certification after casing), and regulated to an industry leading +2s/-2s a day.


Rolex Sea-Dweller Ref. 12660.

The Rolex C.3235 is a new caliber used in the new Sea-Dweller.
Photo by Rolex.


The movement incorporates all the latest Rolex thinking in movements. It is self winding with a power autonomy of 70 hours and features 14 patents in the field of precision, power reserve, resistance to shocks and magnetic fields, convenience and reliability. The new Chronergy escapement, also a Rolex patent is used to combine high energy efficiency with dependability. The escapement is made of nickel-phosphorus, it is also insensitive to magnetic interference. However, we note that Rolex does not publish amagnetic specifications.


The competitive landscape

At S$15,250 (inclusive of GST), the Rolex Sea-Dweller Ref. 126600 sets the pricing and technical standard by which other professional diving watches are measured. In this limited survey of the competitive landscape, we only include participants which are classified for professional diving, meaning saturation diving conditions requiring a solution for the high pressure helium not to blow out the crystal during decompression. While we think that almost all owners of these watches will use them for less demanding tasks of desk diving or swimming and these full featured professional diving watches will never enter a compression/decompression chamber, we recognize the design intent and limit our landscape survey with watches than can be so used.

We begin with the Doxa SUB 1200T Professional (US$2,400 about S$3,260). This latest iteration from Doxa continues the tradition of SUB 300 Conquistador which was the first commercially offered watch to feature a HEV in 1969. As mentioned, Doxa shares the patent with Rolex, and released their SUB 300 Conquistador two years ahead of Rolex’s 1971 commercial release. However, Rolex has been using the HEV in prototype Single Red Sea-Dwellers from 1967, fully testing and confirming their robustness for saturation diving since. The Doxa 1200T Professional is a limited edition of 1200 pieces, and rated to 1200m. It has a bright orange dial, in a stainless steel case measuring 42mm in diameter. However the movement is undistinguished as it uses either (yes, “either” is the actual word used in the official Doxa specifications) the ubiquitous ETA 2824-2, or Selita SW200.

The Omega Seamaster Ploprof Master Coaxial Master Chronometer (S$16,300, full review on these pages soon) is rated to 1200m water resistance in a Grade 5 titanium watch with a bidirectional bezel with a locking mechanism. It features an automatic HEV and the Omega Co-Axial escapement. The anti-magnetic properties of the Ploprof is rated to 15,000 Gauss, which is equivalent to about 1.2 mil A/m. However, the case is even larger at 55mm x 48mm. However, the watch has its own charms and is a favourite of collectors. Watch this space for the link to our full hands-on review soon.

Grand Seiko Hi-Beat 36000 Diver (€12,300 or about S$19,000) which we reviewed in great detail. The GS does not use a HEV of any kind, relying on the extra heavy duty case construction and a special L shaped gasket. We are not privy to how this works during decompression, but we know it does. The case is also larger at 47mm, and the GS case is titanium and rated to 80,000 A/m. However it is priced higher than the Rolex. But subjectively, the finishing on the case, dial, hands and movement is at a higher haute horlogerie level. The zaratsu finish given to the GS is simply breathtaking. Depth rating is lower at only 600m, but that is sufficient even for saturation diving.

Ball Hydrocarbon Deepquest (US$5,700 or about S$7,800) also features an automatic HEV, and is rated to 3000m, with a published amagnetic rating of 4,800 A/m. The Ball features micro gas tubes for the lume, and a titanium single block case measuring 43mm. It is equipped with a ETA 2892 movement.

Sinn has an EZM2 Hydro (was €490 in 2005) with a quartz movement which is rated 11,000 ft/ 5,000 m, but in practice the depth rating is unlimited, as it uses a non-compressible liquid inside the case, and no ingress of helium or water is possible. The EZM2 Hydro is discontinued. In their current collection, the U1 is perhaps the closest, it is rated only to 1000 m but it does not feature any means for helium to escape in saturation diving, so though we mention it, it is not part of the landscape.

Other rare examples include the Hublot Oceanographic 4000, discontinued (was US$19,900 in titanium in 2011) and rated to 4000m, and equipped with an automatic HEV.

As a general survey, the landscape is rather sparse, as the utility for a watch designed for saturation diving is quite limited in the real application market space.

Concluding thoughts

The Rolex Sea-Dweller Ref. 126600 remains a reference standard for saturation diving watches. It is the iconic watch in these deep waters. It performs admirably in desk diving duties that almost all its owners will likely to subject it to. Perhaps add some swimming and possibly scuba diving. Visually, it has immense presence. It looks strong, well built. Powerful even. Aesthetically, it is pleasing and quite beautiful. It demands respect on the wrist. And indeed it wears well. On the author’s 7 inch wrist (wrist measurement revised from 7.5 he recorded during his fat days), it sits comfortably, if a bit large. And is able to slip under the cuffs for a dignified look or be equally at home with in a casual or sporty outfit.


Rolex Sea-Dweller Ref. 12660.

On the wrist the Rolex Sea-Dweller Ref. 126600, on the table in the background the 16600. The 43mm case wears nicely, even for desk diving duties with a suit as it no doubt performs well in deep water saturation diving environments.


And we have good reason to assume with great confidence, the Rolex Sea-Dweller performs equally well under the treacherous conditions that professional saturation divers subject their equipment to.

In addition, we think the detail of the red Sea-Dweller markings will be a feature that collectors will treasure, and the Ref. 126600 might yet be a highly collectible watch.

Rolex Sea-Dweller Ref. 126600 Specifications and Price

Reference 126600
Case: Oyster, 43 mm, steel
Monobloc middle case, screw-down case back and winding crown
Diameter: 43 mm
Material: 904L steel
Bezel: Unidirectional rotatable 60-minute graduated, scratch-resistant Cerachrom insert in ceramic, numerals and graduations coated in platinum
Winding crown: Screw-down, Triplock triple waterproofness system
Crystal: Scratch-resistant sapphire, Cyclops lens over the date
Water resistance: Waterproof to 1,220 metres / 4,000 feet, helium escape valve

Movement: Perpetual, mechanical, self-winding
Caliber: 3235, Manufacture Rolex
Precision: -2/+2 sec/day, after casing
Functions: Centre hour, minute and seconds hands Instantaneous date in apertures, unrestricted rapid-setting. Stop-seconds for precise time setting
Oscillator: Paramagnetic blue Parachrom hairspring
Escapement: Chronergy with optimized energy efficiency
Winding: Bidirectional self-winding via Perpetual rotor
Power reserve: Approximately 70 hours
Bracelet: Oyster, flat three-piece links
Bracelet material: 904L steel
Clasp: Folding Oysterlock safety clasp with Rolex Glidelock extension system. Fliplock extension link
Dial: Black
Details: Highly legible Chromalight display with long-lasting blue luminescence
Certification: Superlative Chronometer (COSC + Rolex certification after casing)

Price: S$ 15,250 inclusive of GST







  1. Gaspar Antonio on

    I have been searching for this watch is several AD´s and the waiting list goes from two to five years! Are we in front of a Sea Dweller Anniversary Mark I? Can this be the same case as the Submariner Fat four Olive bezel? I already enlisted in the shortest waiting list that I found, but the AD told me that the price is going to raise next year, since the demand is very high, is that truth? thank you very much for your advice in advance.

  2. Does it get stuck under the sleeves of a dress shirt due to its thickness? I wear a lot of suits to work regularly and this may be a problem for me.

  3. Great watch but if I’d been the engineering manager at Rolex I would have opted for better solutions for date visibility and crystal popping but that would have required a change to the case that Rolex obviously did not want to consider. Of course others (e.g. UTS, Audemars Piguet) have taken a different path.