Seiko Sumo SPB101J1 Watch Review – A Big Diver That Keeps Proving Its Worth
Back in 2023, after two years of owning my Seiko Sumo SPB101J1, I decided it was time to write a proper long-term review. I’d worn it in every situation—travel, water, work, daily rotation—and thought I’d said everything there was to say. But now, after owning it even longer, I’ve come back to it with fresh eyes. Why? Because the Sumo still doesn’t get the love it deserves.
What really pushed me to sit down and re-examine the Sumo was the sheer volume of new Seiko releases in the last few years—and the price tags that came with them. Mid-tier and higher-end Prospex divers have steadily crept upward, with some of the newer 62MAS reinterpretations coming in at nearly double the Sumo’s price. Meanwhile, the Sumo just keeps doing its thing, still hanging out around the $750 mark.
Is the Sumo still a good deal? Absolutely. Can it hold its own among Seiko’s newer, flashier releases? Without question. In fact, the more Seiko’s lineup evolves, the more this watch stands out for its value, capability, and character.
I bought my Sumo in 2021, and it’s still one of my all-time favorite watches—certainly one of my favorite Seikos. Lately, Seiko released the “Mini Samurai,” which is a cool addition to the lineup. It makes me wonder—if Seiko ever made a slimmed-down Sumo, more people might discover just how good these watches really are. The Sumo design is already fantastic, but a slightly smaller version could open the door for a whole new group of enthusiasts.
A Brief History of the Sumo
The Seiko Sumo first appeared in 2007 as part of the Prospex Professional Diver lineup, initially powered by the 6R15 movement. The early models—like the SBDC001 (black), SBDC003 (blue “Blumo”), and SBDC005 (orange)—quickly developed a following for their distinctive case shape, impressive specs, and approachable price point.
Its nickname, “Sumo,” came from the community, not Seiko. Some say it’s because of the chunky, muscular case paired with a comparatively slim bracelet. Others point to the wide, raised bezel as resembling a sumo wrestling ring, or even to the blocky 12 o’clock marker looking like a mawashi belt. Whatever the reason, the name stuck.
In 2019, Seiko refreshed the Sumo with sapphire crystal, a ceramic bezel insert, and the upgraded 6R35 movement—boosting power reserve from 50 to 70 hours. The SPB101J1 is the modern black-dial version of that refresh, and it’s the one I bought in 2021.
Big on Paper, Manageable on the Wrist
At 45mm, the Sumo sounds huge, but it wears far smaller thanks to Seiko’s excellent case design. The short, curved lugs keep it balanced, and the cushion-style case hugs the wrist. Even on slimmer wrists, it sits comfortably without looking overbearing.
The finishing is classic Seiko Prospex: crisp brushing along the case, polished bevels that catch the light, and a sculpted shape that’s instantly recognizable. It has presence without feeling like a novelty piece.
Movement – Reliable and Capable
The 6R35 movement is an evolution of the 6R15, with the big upgrade being the 70-hour power reserve. It hacks, hand-winds, and has proven to be extremely reliable in my watch. Accuracy isn’t chronometer-level, but it’s well within acceptable ranges for a mechanical dive watch. The long power reserve is a huge plus if you rotate watches—you can leave the Sumo off the wrist for an entire weekend and pick it back up still running.
Legibility and Lume
The black dial is clean, functional, and designed for maximum legibility. Large indices, generously coated with Lumibrite, and broad hands make telling time instant and effortless. The lume is bright and long-lasting—still glowing strong when you wake up in the middle of the night. The bezel has clear markings, firm clicks, and enough grip to operate with wet hands.
The Bracelet Problem (and the Solution)
If the Sumo has one glaring weakness, it’s the stock bracelet. It’s functional, but it feels jangly and cheap compared to the quality of the case and movement. I swapped mine almost immediately for a Strapcode bracelet. The clasp on the Strapcode isn’t perfect—it could be smoother—but the overall feel and fit are a massive improvement. The watch also looks excellent on a quality rubber strap or NATO.
Built to Dive, Ready for Daily Life
The Sumo is ISO-rated for 200 meters of water resistance, has a screw-down crown, and a robust case construction. It’s a legitimate dive tool that can handle salt water, pool days, and everything in between. But it’s also versatile enough to wear to the office or out to dinner, which is part of why it stays in my regular rotation after years of ownership.
Value in 2024 and Beyond
With many Seiko Prospex models pushing well past the $1,000 mark, the Sumo at around $750 retail—and often less from certain dealers—feels like an even stronger value now than it did a few years ago. You’re getting a distinctive design, serious dive credentials, an in-house movement, and the kind of build quality that’s proven over decades of Seiko diver history.
Looking Ahead – Will We See a Slimmed-Down Sumo?
Seiko recently released the “Mini Samurai,” and it’s a fun addition to the lineup. It makes me wonder if we’ll eventually see a “Mini Sumo” for those who love the design but want something smaller. The Sumo as it stands is a fantastic watch, but a more compact version could open the door for an even wider audience to appreciate what makes it special.
Why I Picked It: A bold, character-rich diver that blends classic dive watch DNA with a unique Seiko identity. Tough, versatile, and still one of my favorite watches years after buying it.
Final Take: The Seiko Sumo SPB101J1 is a watch that rewards long-term ownership. It’s not just about specs—it’s about the way it feels on wrist, the confidence it inspires, and the satisfaction it delivers day after day. It’s a great deal in today’s market and absolutely holds its own against Seiko’s newer, more expensive divers. Mine isn’t going anywhere.
Final Thoughts on the Seiko SpB101J1
The Seiko SPB101J1 Sumo is not just a watch; it’s a statement. It’s a testament to Seiko’s ability to create a timepiece that’s large but not overpowering, functional but not mundane. With a design that caters to both the aesthetically minded and the adventurous, the Sumo stands tall in the world of horology, delivering quality and style in a package that’s uniquely its own.
The Complete Guide to Seiko Sumo Models
The Sumo has been part of Seiko’s Prospex lineup since 2007, and while the core design has stayed true, there have been plenty of variations, upgrades, and special editions along the way. Here’s a breakdown of the major generations and notable models so you can navigate the Sumo family tree.
First Generation (2007–2015) – 6R15 Movement
- SBDC001 – Black dial, stainless bezel. The original Sumo and the one that started the nickname.
- SBDC003 “Blumo” – Blue dial and bezel, beloved by collectors for its vibrant color.
- SBDC005 – Bright orange dial, the boldest of the first-gen releases.
- SBDC027 – Limited edition for Seiko’s 50th anniversary of dive watches, gold accents, special dial details.
The first generation established the Sumo formula: 45mm case, chunky indices, 6R15 movement with ~50-hour power reserve, and 200m water resistance.
Second Generation (2015–2019) – Still 6R15, Minor Tweaks
Seiko quietly updated lume, dial printing, and bezel action. The changes were subtle, and many collectors don’t differentiate between late first-gen and early second-gen Sumos.
Third Generation (2019–Present) – 6R35 Upgrade
This was the big modern refresh. Seiko added:
- Sapphire crystal (replacing Hardlex)
- Ceramic bezel insert
- 6R35 movement with a 70-hour power reserve
Key models:
- SPB101J1 – Black dial, ceramic bezel (my watch).
- SPB103J1 “Green Sumo” – Green dial and bezel, subtle sunburst effect.
- SPB125J1 – Black dial with gold accents, limited edition for Seiko’s 140th anniversary.
Special Editions and Regional Exclusives
Over the years, Seiko has released dozens of market-specific Sumos with unique dials, bezels, and case finishes. Examples include:
- PADI Edition – Blue/red bezel, PADI branding.
- Ice Diver Series – Textured dials in glacier-inspired colors.
- Japan Domestic Market (JDM) Only Models – Often with “Made in Japan” dials and slight cosmetic differences.
Sumo GMT – The Newest Twist
In 2023, Seiko introduced the Sumo GMT with a 6R54 movement offering a true GMT function and 72-hour power reserve. It retains the signature Sumo case shape but adds travel functionality.
- 6-month Power Reserve Once Fully Charged
- Beige LumiBrite Hands And Markers
- Stainless Steel Case And Bracelet
- Water-resistant To 10 Bar, 100 Meters (330 Feet)
- WATER-RESISTANT: these water-resistant men’s dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men’s watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: features a durable stainless steel watch case and coordinating silicone watch band
- LUMIBRITE DISPLAY: this men’s automatic watch features a highly-legible display with LumiBrite hands and markers
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men’s watch keeps precise time
- Screw-down crown, screw, see-through caseback, 70 hour power reserve, magnified date window, LumiBrite hands and markers
- WATER-RESISTANT: these water-resistant men’s dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men’s watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: this automatic diver’s watch features a durable stainless steel watch case and rugged black silicone strap
- LUMIBRITE DISPLAY: this men’s automatic watch features a highly-legible display with LumiBrite hands and markers
- 4R35 CALIBER: equipped with the reliable caliber 4R35 automatic movement, this accurate men’s watch keeps precise time
- Case Diameter: 41.7mm
- Case Thickness: 12.3mm
- Case Length: 49.5mm
- Lug Width: 20mm
- Prospex Automatic Diver
- Caliber 4R36
- Silicone Band
- Lumi Brite Hands
- Sapphire Crystal
- WATER-RESISTANT: these water-resistant men’s dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men’s watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: features a durable stainless steel watch case and bracelet
- LUMIBRITE DISPLAY: this men’s automatic watch features a highly-legible display with LumiBrite hands and markers
- 4R35 CALIBER: equipped with the reliable caliber 4R35 automatic movement, this accurate men’s watch keeps precise time
- Case Diameter: 41.7mm
- Case Thickness: 12.3mm
- Case Length: 49.5mm
- Lug Width: 20mm
Blair Witkowski is an avid watch nut, loves pocket knives and flashlights, and when he is not trying to be a good dad to his nine kids, you will find him running or posting pics on Instagram. Besides writing articles for Tech Writer EDC he is also the founder of Lowcountry Style & Living. In addition to writing, he is focused on improving his client’s websites for his other passion, Search Engine Optimization. His wife Jennifer and he live in coastal South Carolina.