The Sea-Dweller was not Rolex’s first foray into niche markets. One might remember the True-Beat, with its jumping seconds, which was made for doctors, or the anti-magnetic Milgauss aimed at scientists. Both watches offered impeccable technical features, but, eventually, they were discontinued given the inherently small size of their respective target markets. It might then come as a surprise that the Sea-Dweller has been around for the past 50 years, focused on a narrow mission statement: go deeper than the Submariner on the wrists of saturation divers and survive anything.

Rolex did not introduce the first dive watch when the Submariner was unveiled in 1954. No, Blancpain had debuted the Fifty Fathoms one year before, and Omega had already unveiled the Marine more than 20 years preior. There is no denying though that the Submariner became the quintessential diver, with its aesthetic becoming the expected form factor for dive watches. Form following function, most of its design was born out of the need to comply with the ISO 6425 standard. Truly, its feat was to nail technical requirements and to achieve a pleasing look at the same time.

When the Sea-Dweller appeared in the late 1960s, the Submariner could already reach an impressive depth of 200 meters/660 feet; in no way was it an inadequate dive companion. Therefore, in spirit the Sea-Dweller was not correcting flaws found on the Submariner but rather extending its underwater utility. Many divers in the SeaLab expeditions had indeed noticed that one strange phenomenon kept on happening to their beloved Submariners – the crystal would often pop out in the decompression chamber after a dive. Obviously that’s no good.

It must be emphasized that we are not talking about casual dives here, but hardcore underwater experiences, as the whole scientific purpose of SeaLab was to study the effects of staying underwater for extended periods of time (the former Astronaut Scott Carpenter achieved 30 consecutive days in 1965). This could only be achieved through saturation diving, and this is where the Rolex Submariner met a serious challenge.

Saturation diving requires the use of helium in the breathing gas mixture, and helium particles would accumulate within the case of a diving watch during prolonged exposure. During decompression, the pressure inside the watch would have to be let out through the weakest point of the watch, brutally expelling the plexiglass as that helium gas forced its way out.

Many prototype watches were made to try to solve this, and they were often nicknamed “Sea-Dweller” watches, given the multi-day stays under water. In the end, a rather simple and efficient mechanism was developed in the form of a helium escape valve on the side of the case. Rolex’s innovation is Swiss patent CH492246, in case you’re interested. By letting the helium particles escape through a controlled mechanism, the exploding plexi issue was solved.

And so began the lineage of the Sea-Dweller, back in 1967. Now, 50 years later, there have been more innovations, more extreme depth ratings, and even a few special editions worth nothing. Here’s a complete look at the five-decade history of Rolex’s most dedicated tool watch.

The very first production Sea-Dweller was the Double Red Sea-Dweller (DRSD). The nickname refers to the two red lines on the dial, which set it apart from the handful of prototypes (read an in-depth article here) that feature just one line of red text. Those are, as you’d expect, called “Single Red” Sea-Dwellers. Interestingly, the helium escape valve is not a defining feature on all those prototypes, but it became the signature of the Sea-Dweller family as we know it today, so we’re starting with the first proper, production reference.

In comparison to the standard Submariner of the time, the DRSD and its 40mm steel case could be distinguished by the obvious valve on the left caseband. It also offered a date display at three o’clock, crucial information for divers measuring their lengthy stays under water. Interestingly, the plexi did not feature the usual cyclops over the date window, as it would not have sustained the underwater pressure (at the time the cyclops was simply glued onto the crystal). Instead there were thick domed plexiglass crystals that collectors today really like.

A few dial versions are known, based on small variations of the red writing. There are classified from Mark 0 to Mark 4, with Mark 5, 6, and 7 being later replacement dials from Rolex. As with most vintage watches, the earlier the configuration, the most valuable the watch – so you can expect prices for Mark 1 and 2 to be many times that of the more common Mark 4, while Single Red Sea-Dwellers almost never appear for sale. By now, a completely correct Single Red would very likely fetch over a million dollars at auction.

Again, the nickname here comes from the dial, as the red lines from the previous models are now printed in white. There is also a distinction between very early Mark 0, and later Mark 1, 2, 3, 4 configurations. The Mark 2 gets a lot of attention from collectors for the arrangement of its Chronometer line – the alignment of the words on the two lines are described as a “rail,” a common feature with the coveted Comex dials. These are called “rail dial” Sea-Dwellers and they’re possibly the most desirable Great White variant. Indeed, the Compagnie d’Exploration was a prime client for the gas escape valve and after purchasing a few Submariners custom-fitted with a valve, it settled on the Sea-Dweller long term.

Red color aside, the “Great White” is very similar to the DRSD: It retained the same 1665 reference number, the same water resistance, and the same case characteristics. The market value of these is far below that of any DRSD, with the exception of those Great Whites with Comex-signed dials. The “Great White” is notably the very last Sea-Dweller to feature a plexiglass crystal, a feature considered by many as a crucial component of a vintage watch.

The “Triple 6” is much less devilish than its name would suggest, yet it represents a radical departure from the aforementioned reference 1665. In many ways, the reference 16660 is the archetype of the “modern” Sea-Dweller, since it features a sapphire crystal – making it among the first Rolex watches to feature it. This element, and its bigger case, allowed it to boast an increased water resistance of 4,000 feet/1,220 meters – double the limit of its predecessors.

A few other changes should be emphasized between the references 1665 and 16660: the date disc lost its silvery finish to become off-white, the bezel became unidirectional, and the helium valve grew in size. The reference 16660 also utilizes the caliber 3035, which offers a faster beat-rate than the previous caliber 1575, and a quick-set feature, adding even more convenience to the Sea-Dweller.

Let’s further break the reference 16660 down into two different breeds: those with the early matte dial with painted indexes and those with the later glossy dial with white-gold surrounds. Indeed, it makes much more than an aesthetic difference, as painted indexes are another feature commonly thought to define vintage Rolex watches. So one can consider the 16660 with both sapphire crystal and glossy dial as the pure modern Sea-Dweller, while the earlier matte dial is more of a transitional configuration offering vintage looks but modern security. Therefore, their value also reflects that situation, with the matte 16660 trailing behind the “Great White” 1665, and the glossy 16660 trading for noticeably lower amounts.

Launched in the late 1980s, the reference 16600 is virtually identical to the late “Triple Six,” maintaining its sapphire crystal and its 1,220 meter water resistance. Over its remarkably long production period, the luminous material evolved from tritium to Luminova, and then to SuperLuminova. You can easily tell which is which by looking at the bottom of the dial – T Swiss T<25 indicates Tritium, Swiss indicates Luminova, and Swiss Made indicates SuperLuminova. Not too tough, right?

The reference 16600 also utilizes the caliber 3135, a slightly improved version of the caliber 3035. It has a longer power reserve and a full-fledged balance bridge, instead of the balance cock. The reference 16600 was discontinued after 20 years in Rolex catalogs, making it the longest lasting Sea-Dweller reference, and an easy model to find pre-owned. As with modern watches, a full set (with original box and papers) is preferable to a “naked” watch, even if it means paying a small premium (in the case of vintage watches, this premium can be drastically higher given the considerable time since the production of the piece).

Introduced in 2008, the Deepsea took the Sea-Dweller to another level, more than tripling its water resistance to an impressive 12,800 feet / 3,990 meters. This obviously is the result of a fair share of engineering marvels, including the 5mm-thick sapphire crystal to support the underwater pressure assisted by a visible Ringlock system that keeps the watch’s thickness below 18mm. And, of course, the watch features a Cerachrom bezel, and the new Chromalight lume. In short, this was the Formula 1 of Rolex divers, in a 44mm case (with titanium caseback to help manage the weight).

A special edition was unveiled in 2014 to commemorate James Cameron’s 2012 expedition into the Mariana Trench. The D-Blue edition (pictured here) was an event in itself, as Rolex almost never does things like this. The watch wasn’t strictly limited in number, and remains available to this day, with its gradient blue dial having found some die-hard enthusiasts. And if you feel 44mm might be too big, this has to be compared to the 51mm measurements of the custom Deepsea Challenge that survived a depth of 10,908 meters on the side of James Cameron’s vessel. That’s no joke.

After a five-year absence, the Sea-Dweller returned in 2014, with the introduction of the reference 116600. Of course, the watch received a bezel upgrade to Cerachrom ceramic instead of the aluminum of the former Sea-Dweller. The case went back to 40mm, with lugs thinner than those of the Rolex Submariner. It offered many details that vintage enthusiasts could relate to, from the Maxi dial with oversized indexes to the full minute markings on the bezel, also found on the vintage MilSub. It also features the modern comfort of the Glidelock adjustment on the clasp and the efficient blue Chromalight lume.

Yet, the reference 116600 is also the most short-lived Sea-Dweller in history, replaced just a couple of years after its initial launch. Despite its technical feats, it never managed to justify its price premium over the Submariner, often solely being identified as the “Submariner without cyclops.” However, as soon as the news of its disappearance hit Basel this year, the second-hand value of the reference 116600 suddenly soared.

Ben reviewed the new reference 126600 in-depth earlier this year, and you probably remember the watch’s most striking novelty: a cyclops over the date. It became the very first Sea-Dweller to feature one, a radical departure from the original reference 1665. Yet, its single red line also offers a charming nod to the first prototype Sea-Dwellers.

Very obviously the watch has grown to 43mm, differentiating it even more from the Submariner, which has stayed at 40mm. Aesthetically, the lug size also grew to 22mm, which preserved the watch’s proportions in the process. The functional upgrades also include the movement, with the caliber 3135 giving way to the caliber 3235. The 3135 features a longer power reserve, higher magnetic resistance, and higher precision. It’s an all-around upgrade.

The new reference is obviously a departure from the original form factor of the Sea-Dweller, but it is mostly a strategic move to make the Sea-Dweller stand out in the current Rolex line-up – especially against the Submariner – and offer an option for a bigger watch without all the technical overkill of the Deepsea.

Now, Sea-Dwellers differ from Subs, GMTs, and Explorers because they were born in the “matte dial” era. This means there is no such thing as a gilt dial Sea-Dweller. That doesn’t sound that meaningful, but consider that the Subs that go for big bucks these days are almost exclusively gilt dial watches from the 1950s and early ’60s. So what makes a really collectible Sea-Dweller? There are a few things that can do it: double signatures, special orders, and age.

Let’s talk about dials first. Any double-signed Sea-Dweller is rare. The example above, retailed and signed by Tiffany & Co., is a very special watch. First, Sea-Dwellers were not exactly commercial products for Rolex – they were issued and assigned to men and women in special forces and technical pursuits. The idea of purchasing a mega-diver at Tiffany & Co. in New York City in the mid 1970s is strange, and that is why they are sought after. Also, the Sea-Dweller has more text on its dial than any other sports Rolex. There are seven lines on the Double-Red – add a Tiffany signature, and you’re up to eight. That’s a lot of text. And while it’s not to everyone’s liking, it sure is strange. And in this world, strange means collectible. There are supposedly some Cartier-signed Sea-Dwellers out there too, but I would be extremely careful about those. Though, really, I’d be careful with almost any double-signed watch unless from the original owner.

Sea-Dwellers were also, at times, given to royal families and royal associates. The watch you see at right above is a 1665 customized for the Sultan of Oman in the 1970s, and it is the polar opposite of the Tiffany watch because there is almost no text on the dial. Instead, you have a Khanjar, the national emblem of Oman. Omani Sea-Dwellers are certainly in the upper echelons of dive watch collecting, and the common thinking is that about 90 Omani Sea-Dwellers with red Khanjars were produced, while between nine and 12 dials like the one above in green were made. This watch sold for 377,000 CHF at Phillips in May 2015.

In addition to double-signed and special commission watches – like those given to COMEX, a topic worthy of an entire dedicated story – the simple truth with Sea-Dwellers is that earlier equals more valuable. Further, those watches with stories to them command significant premiums. The more original period photographs, dive logs, and real-world provenance the better. For example, I can’t remember Jason Heaton ever being more excited than when Philippe-Pierre Cousteau’s Double-Red Sea-Dweller came up for sale. The beat-up Rolex sold for over $180,000 back then in 2014. It was, of course, a very early “patent-pending” example, which are the two words that make any Sea-Dweller fanatic perk up. Just this past week in New York, a “patent-pending” Sea-Dweller MK1 sold for $143,000 a few lots after the Paul Newman Daytona hit $17 million. We’ve seen them go even higher as a good full set.

Still, Comex, Oman, and any special Double-Red have nothing on the almighty Sea-Dweller, the “Single Red.” As mentioned above, the very earliest examples of the Sea-Dweller produced even before the Double-Red watches had just one line of red text on the dial. They were rated to just 500 feet instead of 600, but they are so ungodly rare that any time one surfaces it is serious watch-guy news.

We’ve been writing about them on HODINKEE for over five years and reporting on their records without fail. In 2012, AQ sold one for over $500,000. At that point, it was among the top three most expensive Rolex watches in history. In 2013, Sotheby’s sold one without a bezel for almost $400,000. Earlier this year, Rolex Passion Report published a fascinating look at a newly discovered Single-Red with amazing provenance. The watch was quickly sold to a collector in Asia for an undisclosed price.

It is clear that any Sea-Dweller with a great story of adventure is worth more than one without. Then we have the Comex and Omani watches. Then the Patent-Pending watches, with extra points for an early patent-pending bracelet. But, the holy grail of these mega Rolex divers is without question the Single-Red Sea-Dweller, which is why it was so wonderful to see Rolex close the loop this year by adding just a single line of red text to the 126600.

Special thanks to the many owners who trusted us with their prized personal watches, and in particular Mr. Massena from Vesper Watches, Mr. Kozubek from HQ Milton, Mr. Morgan from IconicWatches, Mr. Ku from 10PastTen, and Mr. Pereztroika from Perezscope. And of course thank you to Rolex for lending us the modern pieces featured here.