Last year, we were treated to the brilliant Sinn T50 series. After trying the three watches out, I became an instant fan of the full-titanium, Goldbronze, and two-tone versions, and the last one made a particularly lasting impression. This time around, the German brand is extending its U-series of dive watches with four new models. Three new U50 versions feature the brand’s Hydro technology (essentially, an oil-filled case). Consequently, these new U50 models follow in the footsteps of their bigger brother, the Sinn UX. On top of that, the brand is also releasing a limited-edition U50 with a luminous dial. It seems like this year is the year of the popular Sinn U50.

The U50 was first introduced in 2020 to much critical acclaim. Press and fans loved that Sinn was introducing a smaller dive watch to its collection. With the U1, U2, and UX models, Sinn has several large 44mm divers that are great, functional timepieces. And that is what we know Sinn for, of course. In everything the Frankfurt-based brand does, form follows function. But we have seen brands create smaller dive watches over time as many regular watch fans do not want a dive tool first and a daily wearer second. That’s why smaller options tend to resonate with a broader audience, and these new U50 models are a logical extension of the brand’s catalog.

Form follows function and leads to a recognizable design

Still, as we’re talking about Sinn, I don’t think the functionality has been toned down to make the smaller size happen. If anything, changes in case dimensions were driven by the technology inside these three watches. Additionally, the design of the Sinn U-collection is distinctive. Overall, Sinn has developed an instantly recognizable design style, but its dive-watch collection stands out immediately. I love that you can recognize a Sinn diver from a mile away.

Sinn U50 S BS Watch 6

Sinn U50 S BS Limited Edition

We first wrote about the U50 in 2020 when the series was announced. Back then, it was about combining Sinn’s technologies to create the smaller brother of the U1 from special German submarine steel that is Tegimented for improved scratch resistance. In 2021, Sinn released the rather spectacular U50 S Mother-of-pearl limited edition, combining a stealthy black aesthetic with a blue mother-of-pearl dial. A year later, Mike reported about the limited-edition U50 S BS that combined the same black aesthetic with a blue gradient dial. These additional models perfectly showed that the U50 could look great even if it broke away from its more hardcore dive-tool aesthetic.

The specs of the three new Sinn U50 Hydro watches

So, let’s look into some of the specs of these versions. As mentioned, there are three new U50 Hydro models. The first is the Sinn U50 Hydro Tegiment, the second is the U50 Hydro S, and the third is the U50 Hydro SDR. They are all the same watch with some noticeably different elements. All three have a 41mm case made of German submarine steel that is 11.8mm thick with a 20mm lug spacing. The lug-to-lug length is not mentioned in the press materials, but it’s safe to say it will be in line with the other U50 models at 47mm. The case utilizes Sinn’s Tegiment technology for better scratch resistance and features a screw-down crown at 4 o’clock and a screw-in case back.

Sinn’s Hydro technology

Compared to the regular U50 models from 2020, which are 11.2mm thick, the cases of these three new ones are slightly thicker. This is due to the implementation of Sinn’s brand’s Hydro technology, meaning that the cases are filled with oil. Doing so allows the wearer to read the time from any angle without distortion or reflection, prevents the watch from fogging up, and replaces the air inside the case, making it incompressible. These benefits tremendously increase the practicality of the watch when diving at great depths. Like the Sinn UX models, all three watches have a 5,000m water resistance rating. At 10 times that of the standard U50’s 500m depth rating, that is super impressive.

Another big change that comes with the oil-filled cases is the movement inside. The Hydro technology requires a change from a mechanical caliber (the Sellita SW300-1 that powers the regular U50 models) to a quartz one. In this case, that’s the Ronda 715Li movement. It is antimagnetic to 1,000 gauss, has a 60-month battery life with an end-of-life indicator, and is functionally reliable from -20°C to +60°C. The movement is a standard three-hander with a date indicator at 3 o’clock.

The Sinn U50 Hydro Tegiment

If we then move on to the three different models, we’ll start with the U50 Hydro. This “basic” version comes with a bead-blasted stainless steel case and bezel that have undergone Sinn’s Tegiment hardening process for better scratch resistance. The bezel features a 60-minute scale with red minute markers, black numerals for every five minutes, and a white inverted triangle for the 60-minute indicator. Moving inward, we see a deep black dial contrasted by white markers and white sword-style hour and minute hands, all treated with lume. The seconds hand is bright red with a hint of white lume, the Sinn logo is white, and the Hydro U50 model name and “Made in Germany” text are bright red. These elements create an overall black, white, and red color scheme that we know all too well from Sinn.

Sinn always offers several options for straps and bracelets. The watch is available with a bead-blasted bracelet with a folding clasp, a selection of leather straps, and a variety of silicone straps with either a regular folding clasp, small folding clasp, or pin buckle. Speaking of clasps and Sinn novelties, the brand also announced a new clasp with toolless micro-adjustment. Additionally, we know the H-link bracelet will improve in quality as well. The Sinn U50 Hydro Tegiment will be €2,150 on a leather strap, €2,360 on a silicon strap, and €2,375 on the stainless steel bracelet.

The Sinn U50 Hydro S

The second of the three models is the U50 Hydro S. This stealthy version is treated with a black hard coating based on its fully Tegimented case and bezel. As the bezel is black, the 60-minute scale is executed in red and white, and bright red is used for the minute markings. Additionally, there is a white rectangle and Arabic numerals at every five-minute marker. The dial is the same as on the previous model, so there’s no need to rehash its details.

The variant is also available with various strap and bracelet options. The first is the stealthy black Tegimented bracelet, and then there are several leather and silicone straps with a pin buckle, a small folding clasp, or a regular-length one. The nice thing about the clasps on all the silicone straps is that they also feature the Tegiment hardening treatment and black hard coating. The Sinn U50 Hydro S will be €2,550 on a leather strap, €2,870 on a silicone strap, and €3,010 on the black Tegimented steel bracelet.

The Sinn U50 Hydro SDR

The last of the three variants is a combination of the first two. It comes with a bead-blasted stainless steel case with a black bezel. As you’d imagine, the case and the bezel have undergone the same Tegiment hardening process for extra scratch resistance. The black bezel is the same as on the U50 S, and the dial one from the two other models. This U50 Hydro SDR is the perfect marriage of the first two versions. It will go for €2,240 on a leather strap, €2,450 on a silicone strap, and €2,465 on the stainless steel bracelet.

I think this is the most exciting option. Pair it with a gray silicone strap, and you will have an incredibly competent and attractive watch. Sure, it doesn’t beat the T50 GDBR in all its two-tone bliss, but it looks fantastic. Still, let’s not forget that making beautiful watches is not number one on Sinn’s priority list. This trio of watches has turned the U50 into a different beast by adding the Hydro technology and increasing the water resistance to 5,000 meters. It makes these timepieces veritable beasts of the deep.

The Sinn U50 S L

But that’s not all because the release of a new limited edition accompanies the that of the three new U50 Hydro models. The new Sinn U50 S L is the next in the line of black U50 models with a special dial. After the mother-of-pearl and blue-dial editions that I mentioned earlier, it’s time for one with a luminous dial. As the mechanical U50, the watch comes with a slightly slimmer case that measures 41mm in diameter, 11.2mm in thickness, 47mm long, and 20mm between the lugs. The watch is also made of Tegimented German submarine steel with a black hard coating.

This creates a high-contrast backdrop for the luminous dial, which Sinn utilizes an innovative method to create. First, luminous paint gets specially cast into a mold where it hardens into one solid layer. After that, it is fused to a ceramic component for stability and joined to a metallic dial base. Once combined, the dial then receives its ultra-legible printed black markings. This process results in a dial with a large surface area and a high concentration of luminous material.

A limited edition of 500 pieces

As you can see, the dial lights up bright blue in the dark. The black hands and markers provide equally good contrast regardless of lighting conditions, ensuring great readability at all times. As you can see, the key marker on the bezel is also treated with lume and lights up in the dark. Overall, it is a striking and impressive look. Inside the case, you will find the self-winding Sellita SW300-1 that also powers the other mechanical U50 models. It operates at a 28,800vph frequency and offers a 42-hour power reserve.

This special 500-piece limited edition will be available with the same wide selection of leather straps, silicone straps, and the black Tegimented bracelet. The watch will be €2,790 on a leather strap. On a silicone strap, it will be €3,110, and on the black bracelet, it will be €3,250. I love that Sinn has created a U50 with a fully luminous dial, and I expect that all 500 pieces will go fast. I hope that the brand will also create a regular stainless steel version with this dial. A model like the limited-edition U50 DS with a luminous dial would be quite a surprise.

Final thoughts on the new Sinn U50 models

But I am drifting off here. The new lume-dial U50 is a clever and nice follow-up to the previous black U50 limited editions with special dials. I have to give Sinn credit for creating a series of limited editions with a visual theme. It’s a fun series, and I can’t wait to see the luminous dial in real life. Knowing how thoroughly Sinn creates something new, I expect this dial to be spectacular.

The three new U50 Hydro models are logical additions to the lineup. Since the Sinn U50 came out, it has been a popular line for the German brand. By incorporating the Hydro technology and increasing the water resistance to 5,000 meters, Sinn adds three more competent divers to the collection. Will they be more popular than the mechanical U50? I don’t expect them to be. Still, every time I see an oil-filled Sinn, I sense that little bit of magic that makes these models very cool. And I’m sure a hands-on review will reveal more of the magic of these three new Sinn U50 models.

For more information on these new U50 variants, visit the official Sinn website, and let us know which one is your favorite in the comments.

Watch specifications

U50 Hydro Tegiment / U50 Hydro S / U50 Hydro SDR
Black dial with white luminous markers and red and white text
Case Material
German submarine steel with full Tegiment treatment (U50 Hydro Tegiment), black hard coating (U50 Hydro S), or black bezel (U50 Hydro SDR)
Case Dimensions
41mm (diameter) × 47mm (lug-to-lug) × 11.8mm (thickness)
Case Back
German submarine steel, screw-in
Ronda 715Li: quartz movement, antimagnetic to 1,000 gauss, 60-month battery life, end-of-life indicator, functionally reliable from -20°C to +60°C
Water Resistance
Choice of stainless steel bracelet (20mm width) with Tegiment hardening or a selection of leather and silicone straps
Time (hours, minutes, seconds), date, 60-minute dive bezel
U50 Hydro Tegiment: €2,150 (leather strap), €2,360 (silicone strap), €2,375 (stainless steel bracelet) / U50 Hydro S: €2,550 (leather), €2,870 (silicone), €3,010 (black steel) / U50 Hydro SDR: €2,240 (leather), €2,450 (silicone), €2,465 (steel)