Watch Face & Crystal
The watch face on the SeaDweller Ref 16600 appears smaller that the face of the GMT II. In fact, it is 1mm smaller. Notice in the picture on the right how a GMT Bezel ring is much larger in diameter than the SeaDweller bezel. Because of the increased thickness of the watch crystal (3mm), the chapter ring on the SeaDweller is steeper adding to the effect of the smaller watch face. The thicker chapter ring is a tell tale sign of a true dive watch later reproduced in the SeaDweller 4000 and SeaDweller 43 so there is more surface area for the watch crystal to rest upon under pressure.
With the thicker crystal on the SeaDweller, a cyclops lens over the date is not installed. No cyclops makes reading the date a little easier from the side. Initially, people thought the thicker crystal combined with the cyclops would not work because of the optics involved, but in reality, Rolex could not find a method to affix the cyclops that could withstand extreme underwater pressure. Up until March 2017 when Rolex released the SeaDweller 43 ref 126600, Rolex SeaDwellers did not possess a cyclops.
Watch wearers have debated the need for a date wheel feature on a diving watch, but the date feature makes the watch a much more versatile watch for uses outside of diving. When I had the No-Date Sub (Ref 14060), I surely missed the date feature and thus was relegated to a weekend wearer. Even without the cyclops lens the date is still readable and functional.
The watch face on the GMT appears wider and bigger. The lettering on the GMT face, although very readable, appears not quite as bright as the SeaDweller. The extra line on the SeaDweller indicating 4000ft/1220m depth rating brings more attention to the bottom of the watch face.
A great tutorial for setting and using the GMT functions is posted here.
The bezel on the SeaDweller is unidirectional only rotating counter-clockwise, whereas the GMT is intended to be bidirectional. The SeaDweller bezel is much tighter to rotate than the GMT and the No-Date sub (Ref 14060) that I owned previously. I attribute the tightness to the thicker crystal adding to the drag, as well as the bezel just fitting tighter. There is little play between the bezel and the watch case when the bezel is pushed down.
The GMT bezel is slightly wider. The silver lettering gives a different feel than the silver lettering on the GMT. Both GMT and SeaDweller lettering picks up the color of the watch case, but the black background on the SeaDweller bezel matches the black face making it appear integral to the watch. Two different looks for two different design intents and purposes.
The GMT bezel is designed to be bidirectional. The GMT bezel is certainly easier to rotate counter-clockwise. Although the bezel can rotate clockwise, it does not move easily. I read on one of the Internet boards that Rolex is replacing the bezel click-spring with a longer one that makes it easier to move the bezel clockwise. I have not seen this spring, but will investigate on my next visit to a Rolex Service Center (RSC). It is worthy to note that the re-designed GMT II ceramic (Ref 116710) case has a new bezel that rotates on four ball bearings and moves easily clockwise and counter-clockwise similar to a YachtMaster and the redesigned Turn-O-Graph (TOG) bezel. The TOG bezel slides without any clicks and the newly redesigned GMT II has a click on UTC every hour.
One of the advantages of the Ref 167xx GMTs are the ability to change the bezel insert. I swap between red-black and red-blue every few months or so. A great tutorial on changing a GMT bezel insert is posted at https://www.rolexforums.com/showthread.php?t=8561.A schematic of bezel inserts and part numbers is posted here (right click and save the .pdf to your desktop).
The bracelets on both the GMT and the SeaDweller have solid end links which are quieter than the traditional end pieces that were on my No-Date Sub. When cycling, the traditional end-links rattled.
I discovered that the extra watch head weight makes adjusting the bracelet somewhat more finickey. Click here to see how I resolved this using a rubber pad.
What distinguishes the difference between the two bands is the clasp. The GMT clasp is similar to the traditional clasp found on the traditional DateJusts.
One distinguishing difference between a GMT and a DateJust is the OysterLock feature, although the original GMT’s had a similar clasp to the DateJusts of the day. Because the clasp is smaller and thinner than the SeaDweller, it is slightly more comfortable when used as a desk watch. The clasp does rests upon a desk comfortably, especially when keyboarding.
|To release the diver's extension, turn the loose oyster link 90 degrees, then push in towards the clasp cover.|
The SeaDweller Ref 16600 clasp is both thicker and the cover is longer in order to accommodate the extension link used to lengthen the band such that the bracelet can fit over a wetsuit. The clasp hinge is the same length as the GMT and other Rolex models, but the SeaDweller Ref 16600 clasp appears longer as the clasp cover is longer. The extension link is held into the clasp cover by using a hook that fastens a link to the spring bar that holds the extension link in the clasp. Earlier extension Submariner and SeaDweller extensions were held by compression from the sides of the clasp cover. The extension link in my No-Date sub (Ref 14060) was not held as securely as this new “push-the-O” design, as well as the extension link rattled. The clasp on the Ref 14060 was a true "tuna-can" clasp. The thicker clasp on the SeaDweller is much more of a presence and does not rest as comfortably when used as a desk watch.
The Crowns & Setting Time
The crown on the GMT is the traditional twin-lock design where there is a rubber gasket in the tube and inside the crown. The thinner crown make winding and setting the watch a little more of a delicate affair than the Triplock crowns found on the SeaDwellers.
The Triplock crown utilizes four o-rings to insure waterproofness. One o-ring is located outside of the tube, one in the crown, and two inside the tube. The larger tube makes it easier to screw-down the crown and will be a welcome addition to the GMTII stainless line.
SuperLuminova is a great feature on all the professional Rolex lines. The Japanese took Luminova to the next level by developing SuperLuminova. My GMT and SeaDweller glow reliably at dusk and at night. My No Date Sub (Ref 14060) had 10 year old Tritium and was barely legible in the dark.
During a Grand Canyon rafting adventure with my GMT, the watch glowed all night after being in the desert sun all day. The SuperLuminova on both the GMT and the SeaDweller is much brighter and legible than the glow on the F series Tour-O-Graph that I owned.
Yep, I keep the hologram on until it wears off. I mistakenly tried to take the hologram off my F series TOG only to scratch the back of the watch. Let nature take it course with holograms (about three-months with everyday use).
I did notice that the hologram can be slid off after a few weeks of use. Just push the hologram with both thumbs to the side without stopping. The hologram will slide off without tools or chemicals.
Height, Weight, & How It Wears on a 6.75" Wrist
Just as how the GMT and SeaDweller look different, they also wear different. The weight of the GMT is 127g whereas the SeaDweller is 147g. The weight combined with the increased thickness and height of the SeaDweller, makes the watches feel different when worn.
The GMT fits comfortably and close to the wrist with its 12mm height. Because the caseback is not as thick and deep on the GMT as both the Submariner and the SeaDweller, it fits close to the skin. The thinner caseback combined with the smaller crown makes the GMT crown less likely to dig into the back of the wearer’s hand, especially when the bracelet is worn loose. I notice that when one pushes the GMT caseback with both thumbs, one feels very subtle flexing. I noticed the same type of flexing with my DateJusts. One will only notice the flexing of the caseback when there is a Submariner or SeaDweller nearby to compare. Try it the next time one visits an AD and have a DateJust/GMT and a Submariner/SeaDweller on the counter.
Notice in this picture that the lugs of the SeaDweller have more of a curve/contour to them than on the GMT. The GMT has somewhat of a flatter case than the SeaDweller. The caseback on the SeaDweller is thicker allowing for engraving as well as making the watch sit higher than the GMT.
The increased height (14.65mm) and weight of the SeaDweller makes the watch slip over the wrist more so than the GMT. There is much more "watch flop" on the SeaDweller than the GMT. Subsequently, I wore the SeaDweller tighter than GMT. Even with the increased tightness and weight, the watch sat okay on my 6.5” wrist. If I wear the bracelet one notch looser, the crown would dig into the back of my hand and there would be much more watch flop. After wearing the SeaDweller for a few consistent weeks, I found the increased weight, specifically the top heaviness, too much to bear and traded the SD for a Submariner. One of the notable distinctions separating the Submariner from the SD and the GMT is that the Sub has 4 1/2 links on the 6 o'clock side rather than five full links that the GMT and SD have. If the SD had the same 4 1/2 link combination as the Submariner, I believe the clasp would stay centered on the underside of the wrist rather than being slighly offset. For large wristed wearers, this point is moot as the clasp is centered and the watch head has a bigger platform to rest. Having a half-link on the SD, and a braclet that helps counter balance the top-heaviness of the watch such as the solid-linked bracelets found on the Anniversary GMT's, the TOG, and Daytona, would have helped the SD feel more balanced on the wrist.
The SeaDweller uses a Rolex in-house 3135 movement that has been well chronicled for its robustness, and the GMT 16710 uses the 3185 or 3186 movement that is very similar to the 3135 but with an additional 24 hour hand and the hour hand that can roll forward or backwards independently of the other hands. The SeaDweller is approximately 1-2 second fast/day after two weeks of constant use (and ownership) and the GMT is approximately 3-4 seconds fast/day.
Both of these watches have special places in the Rolex line because they do what they are designed to do, and do it very well. I like the wider face of the GMT, plus I can monitor when Tour de France stages start in real time, I find myself gravitating back to it. The SeaDweller is a much more robust watch. When I remove the SeaDweller from my wrist, it feels like something is missing. The body seems to assimilate the weight of the watch and misses it when the watch is removed. The GMT is noticeably lighter and does not have this effect.
WIS' have noted that the GMT fits better under a shirt cuff than thicker watches. I have found that the SeaDweller fits just fine under most dress shirts with fitted collars and cuffs. although the GMT can sit in a little more stealth mode.
My experience with the SeaDweller was a good one. Although I traded it for a Submariner, there are good reasons for why the SeaDweller is a classic. Other than how the SeaDweller sits on small wrists, both the GMT and the SeaDweller have distinct qualities that are equally important and to decide between the two is hard.