Why the Sinn U1 S Is the Best Diving Watch Available. Trust Me, I’m an Expert.

Posted by Nick L. on April 21, 2021

We’ve all seen those commercials. They go something like “You’re not a doctor!” “No, but I did stay at a Holiday Inn Express last night.”

Well I’ve never been deeper in water than the bottom of a swimming pool, but I have over 1000 posts on a watch forum, and I even write watch blog articles. That officially certifies me as a dive watch expert. Every watch collector worth his or her wet suit extension knows what it takes to make a dive watch ISO 26262 compliant, and would never forget to vent their helium release valve after taking a shower.

This why I’m qualified to say that the Sinn U1 S is the best diving watch that money can buy. Sure, its new baby brother, the U50 has been getting all of the hype, but it’s not a better dive watch. You’ve all been there, you’re diving in the ocean, and you reach 500m deep. You stop to wave hello to a lobster, and suddenly the motion of the of your arm increases the pressure of the water, crushing your crystal. Your watch is ruined.

This is one area out of many that the U1 bests the 500m-rated U50. The U1’s rating of 1000m is at least 50m deeper than I typically go, giving me plenty of margin. Sinn also makes the oil-filed UX, which is rated to 12,000m, but first, who needs to go that deep, and second, it is quartz. Try finding a store with a battery at the bottom of the Marinara Trench.

Note to the reader: If you haven’t figured it out yet, this article contains some satire. It is a genuine review, and I really did buy a Sinn U1 S. Just any take any of the “facts” related to diving with a grain of salt. They are jokes poking fun of ourselves as watch enthusiasts, and the concept of most of us owning a dive watch.

Why the U1 S?

I’ve owned a few Sinn watches, and on the wrist they always add up to more than the sum of their parts. The U1 had been on my radar for a while, and the recent coverage of the U50 only stoked the flames. Since my 600m-rated Omega Planet Ocean was really limiting my diving, I decided to take the plunge on the U1.

If you read my article “The Top 6 Watches to Wear During the Apocalypse,” you already know that the Sinn U1 Camoflage has some serious chops. So why did I go with the “S” model for diving? Simple! Camo is not going to do you much good when there isn’t a tree for miles. The Black Hard Coating on the case and bezel of the “S” model will avoid reflecting light into the eyes of a baby shark, possibly enraging its mommy shark.

And if you do encounter a shark, the S model is fully Tegimented (as opposed to only the bezel on the camo model), which means that a hardening process is applied to the outer surface of the watch, making it more resistant to scratches. Tegimented steel has a hardness of 1,200 Vickers on Moe’s scale. Shark teeth have a hardness of 500, while regular stainless has a hardness of around 200. You do the math, your wrist will thank you!

Additionally, all of the “U” series Sinn models are made from the same steel as German U-Boat submarines (seriously!). Not only is it extremely resistant to corrosion, but if you encounter a broken submarine while diving, you might be able to help the crew repair it. Who knows, maybe they will give you a ride in a sub for saving their asses?

First Impressions

I purchased the U1 S used from a member of a watch forum. When it arrived a few days later, I was very excited upon opening the box. Besides the aforementioned benefits of an all-black watch, it looks bad ass! The U1 case, bezel and crown have a matte finish which is smoother than the bead blasting you’ll see on other watches. When you combine this with the coating, it almost makes the watch look like black plastic.

This, combined with the size of the watch gives it almost the look of a high end GPS watch on the wrist. That is until you feel all of its 133 grams (head only). The U1’s heft, combined with the smooth matte finish gives it a very high quality feel, plus it should help you sink to your desired depth more quickly when diving.


At 44mm in diameter, and 14.7mm thick, the U1 is not a watch for the faint of heart or wrist. The black color of the S helps mask the size, but white paint on a bezel that overhangs the case still makes it wear big. Luckily the lugs are compact (50.5mm lug to lug), so it won’t overpower even average-sized wrists.

The case hides its height visually with chamfers on the edge of the bezel and bottom of the case, but a thick case-back adds to the vertical dimension.

In between the lugs are the letters SUG. This is the abbreviation for the company that makes the U series cases for Sinn out of that submarine steel.

Additionally, the U1 is low-pressure resistant. What this means is that it is built to withstand the rigors of saturation diving without the need for a Helium Escape Valve (HEV). This was a huge reason for me to buy the U1. I’ve lost count of how many watches I’ve had fill with water due to automatic HEV failure, and I’ve had to buy 3 new crystals for my Omega due to forgetting to open its screw-down HEV when decompressing.


The U1’s 60-click uni-directional bezel is quite easy to grip, and turns with little resistance. Unlike on a watch like a Tudor Pelagos, the click feeling is not precise, but I think it perfectly fits with the character of the watch. The bezel feels like a rugged tool rather than a precision instrument. Additionally, the two colors of paint popping off the black background look cool and make it quite legible.

The bezel is also what Sinn calls a captive safety bezel. This means that rather than being held on only by friction, the bezel is secured by screws. Not only does this make it about impossible to knock the bezel off, it also means that it can be easily replaced if needed.


The large, signed crown is very chunky and easy to grip, yet it is offset to avoid risking popping a hole in your diving glove. Another reason that the U1 is the best dive watch.


One of the benefits of the larger size U1 over the U50 is a very large dial, which should be easier to read on land or under water.

The green-glowing lume on the U1 is fairly bright, but is not shockingly bright when fully charged. At first, you might be disappointed if you’ve owned a Seiko, or a watch with Superluminova C3. It does seem to stay consistently bright throughout the night, and I’m always able to read it. Plus, because the hands are so large, and stand out against the matte black dial, it is easy to read even after the lume dims. I’ll accept that trade-off to keep the stark white hands and indices rather than the cream color of stronger lumes.

Also, I’ve read that too bright of lume can attract attention from distant jellyfish, so this maybe a purposeful design by Sinn.


As any Jared’s: the Galleria Of Jewelry salesperson will tell you, orange is the most visible color underwater. The Sinn uses a bright red color which is next to orange on the color spectrum. This allows its hands to be very visible when at sea, without being as distracting as orange would be.

In all seriousness, the U1 is hands down the most legible watch that I have ever owned (other than the Par Weber Coefficient in low light conditions). Not only does this make it a great dive watch, but also a fun watch to wear when on deck. The sizing and shape of the hands and hour markers, combined with the contrasts of red, white and matte black make it extremely easy to read.


The U1 has a flat sapphire crystal that is anti-reflective on both sides. The legibility is fantastic at any angle, and the AR coating has to be the best in the business. The only small downside is that it picks up a lot of fingerprints, and I’ve heard that it can be scratched easily. I’ll take that tradeoff.


Unfortunately my pre-owned U1 was sold separately from its original strap or bracelet somewhere along the way, so I can’t review that. Luckily, it looks fantastic on a wide variety of 22mm straps. I’ve been mostly wearing it on a red rubber quick release strap or a black wave rubber quick release strap, both with a black buckle to match the case. If you like the look, you can buy them from my website straphabit.com.


A reliable automatic movement that doesn’t require a battery and can be easily serviced is key to the best dive watch in the world. The U1 uses a Sellita SW 200-1, which fits the bill perfectly. It uses 26 jewels, operates at 28,800 vph, and is hacking. The power reserve is roughly 38 hours.

Be Honest, do you wish you had gotten a U50?

At the time that it was released, I was very excited about the U50. I have yet to try one on, but I love the U1, and don’t regret the decision. One reason is that at the time I bought it last year, U50 availability was very limited. Even today, used models are available infrequently, and when they come up, they trade for around MSRP. The older model U1 is much easier to find pre-owned, and thus is less expensive.

Additionally, I think that the bigger size fits the character of the U-series better. It’s a big and bold watch with Lego-like hands. It deserves to have a big and bold case. This is not a watch to be worn with a dress shirt and a tight cuff anyway.


Even though it was released in 2005, the U1 line still looks quite modern. In a time where it feels like every watch released is a reissue from a brand’s back catalog, it is refreshing to wear something that looks like it is from today, and more importantly could not be confused with anything else

The U1 S is the watch that I have worn the most since I bought it, and is (in my expert opinion), the best dive watch available.

Your Thoughts?

What do you think of the U1 S? Is there a better dive watch available, and if so, what do you think it is? We’d love to hear from you in the comments.

And if you enjoyed this review, please check out my website, straphabit.com! Your support helps me to continue creating reviews like this one!


  • Name: Sinn U1 S
  • Reference Number: 1010.020
  • Price: $2,840/$2,980 on Strap/Bracelet  (for the all-black S model)
  • Dimensions: 44mm diameter, 50.5mm lug-to-lug, 14.7mm thick, 22mm lug width
  • Movement: Sellita SW200-1
  • Water Resistance: 1,000m
  • Crystal: Sapphire with clear AR coating on both sides
  • Crown:  Screw-down
  • Bezel: Unidirectional, tegimented steel 60 clicks
  • Strap/Bracelet: Tegimented stainless steel bracelet or silicone strap with deployant (standard straps were not available, StrapHabit FKM Rubber shown for the review).


Subscribe to WatchCharts Weekly

Read about our coverage of the watch market, new watch releases, infographics, and more!

Never miss a deal. Get our app!

- OR -

Text me the FREE download link

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.