Diving with the Sinn U50, The Smaller Version of THE German Dive Watch

If you’re on this website, reading the latest article in my diving test series, there’s a pretty good chance that you have at least a passing familiarity with Sinn watches. There is an equally good chance that most of your non-watch-nerd friends, family, and colleagues do not. Flying just under the radar, Sinn has been producing beautifully well-made toolwatches for over 60 years now. If there’s any brand that functions as a nod and a wink and a horological secret handshake, it’s this Uhrmacher aus Germany. And that handshake has to be done with an iconic diving instrument (it really is that) on the wrist, a Sinn U1… Or should it be its smaller, more versatile brother, the Sinn U50?

A Bit of History

Founded in Frankfurt in 1961 by former WWII pilot and flight instructor Helmut Sinn, the brand initially focused on the manufacture of navigation clocks and pilot chronographs. In the 1960s and 1970s Sinn manufactured watch cases for military and consumer use, including the notable Heuer/Sinn Bundeswehr chronograph. In 1985 German physicist and astronaut Dr. Reinhard Furrer wore the Sinn 140S during the D-1 Spacelab mission, making it one of the first automatic chronographs worn in space. 

In 1994 the company was acquired by an engineer named Lothar Schmidt who had previously worked at IWC and had been in charge of the technical production development of the newly re-established A. Lange und Söhne brand. Schmidt renamed the company “Sinn Spezialuhren GmbH” and initiated a major strategic reorganisation to lead the company into the future and enhance its technological expertise. The first watch in this new era of technical endeavours was the 244, made of titanium with magnetic field protection and featuring a freely oscillating suspended movement.

Many technological achievements would follow, including AR-dehumidifying technology, to keep those crystals crystal clear; HYDRO technology which is filling the entire watch case with oil to replace the air, thus making it virtually immune to pressure; and the famous TEGIMENT technology, which is a hardening of the outer layer of the material to make it ultra-tough and resistant to scratches and dings. According to the brand their watches are worn by “pilots, divers, firefighters, emergency doctors, rescue workers, special units of the German police department and armed forces such as the GSG 9, Germany’s commando frogman force KSM (Kommando Spezialkräfte der Marine)”.

In 2005 Sinn released the U1, their flagship modern dive watch. While lauded as a well-designed, meant-to-be-used toolwatch, many non-diving watch aficionados felt the 44mm beast was just a little too big for daily wear. Although it took them 15 years, Sinn finally heeded these calls and, in 2020, released the U1’s little brother, the U50 – there’s even the T50 now, in titanium. 

The Watch

The Sinn U50 is a 41mm in diameter, 11.2mm thick dive watch crafted out of high-strength, seawater-resistant German submarine steel. While 3mm smaller than its big brother might seem like a tiny amount to the layman, in the minutiae-obsessed world of watches it can make a sizable difference. It’s also 3mm thinner than the U1 which probably helps the wearability even more than the diameter shrink.

All the design cues of the U1 are intact, from the bead blasting of the entire case, bezel, and bracelet to the matte black, hyper-legible dial. The bezel is captive, meaning it’s held in place by screws (rather than tension like most dive watches) to prevent it from popping off even under the most stressful usage. The flat sapphire crystal is so anti-reflective that at most angles it seems like it’s not even there, which is equal parts enchanting and alarming. A 4 o’clock screw-down crown and a solid caseback keep things watertight down to 500 metres, a pretty remarkable feat for a watch just 11mm thick. 

Down in the engine room, you will find the Sellita SW300-1, that ubiquitous workhorse clone of the ubiquitous workhorse ETA 2892. Beating at 28,800 vibrations/hour with a power reserve of 42 hours, this easily repairable or replaceable movement is a solid choice for a hard-wearing tool watch. 

The watch is available in various configurations of the Tegiment technology mentioned above. The standard version has a Tegimented bezel and standard submarine steel for the case and optional bracelet. You can upgrade (for a price of course) to a fully Tegimented version where all facets are treated, including the bracelet. Both options are also available on a Sinn rubber strap with a deployant clasp instead of the bracelet. 

On Wrist

As a longtime admirer of the U1, and a card-carrying member of the Dainty Wrist Society, I was powerless to avoid picking one of these up as soon as possible. On the wrist, the Sinn U50 delivers everything promised and more. The fit and wear are pure goldilocks, virtually perfect in every way.  It has just enough heft that you won’t forget you’re wearing a high-tech mechanical tool, but svelte enough to pass through even the smallest door frame with ease. You know what I’m talking about. I opted for the fully Tegimented version of the bracelet and have no regrets. The H-link bracelet is as beautifully designed and recognisable as the rest of the watch’s Teutonic design. 

A word about the Tegiment tech: as one of the technological innovations Sinn is most known for, it seemed like it would be a shame to not go for that option, and boy am I glad I did. I have been wearing this watch pretty regularly for almost 18 months and there is nary a scratch in sight. Seriously, not a single one. Even on the bracelet clasp where you would find all the standard desk-diving scuffs and scratches, there is nothing. It is surely some sort of sorcery. Now let’s take it diving. 

In the Water

While the Sinn U50 looks and wears great topside, strapped down over a wetsuit, it truly comes into its element. It nestles down nicely into the neoprene, becoming even more streamlined and ready for its duties as a dive timer. The no-nonsense design fits right in with the hi-tech looks of modern diving gear and computers. It’s less a piece of jewellery and more a piece of kit, the bead-blasted finish offering no ostentatious sparkling or signs of luxury. 

We took the U50 on a few dives in the daytime and one at night down in the Florida Keys. While its stark design cues might be more aesthetically compatible with some northern cold-water drysuit diving, this would do just fine. Underwater the watch does everything you could ask of it. Knowing there is a r calibre beating inside sets the mind at ease that the timing will be spot on. The high contrast of the hands, dial and bezel make the occasional quick time check feel like second nature, giving you all the information you need and nothing you don’t. Once night set in the U50 continued to perform admirably; a quick charge from the torch and the lume continued to glow throughout the dive, keeping everything bright enough to be quickly legible.

The only thing that could make this a better dive watch would be the addition of a quick-adjust bracelet clasp of some sort, to compensate for the compression and expansion that happens to wetsuits at various depths. Otherwise, this is a 10/10 modern dive watch that is destined to stay near the top of my list of watches I want to wear while actually scuba diving, for years to come.

Final Thoughts

Though it took Sinn 15 years to come around and make a slightly more wearable dive watch, in the three short years since they have already iterated on this multiple times. They have released a few limited editions and different colourways, then some versions in titanium as the T50, and then the most recent addition, the oil-filled U50 Hydro (which is quartz, of course). As they seem to be in high gear making up for lost time, it’s an exciting time to be a Sinn fan. From EUR 2,475.

For more details, please visit sinn.de.