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Seiko’s 2023 Prospex PADI “Great Blue” trio comprises the 45 mm King Turtle SRPK01, the 43.8 mm King Samurai SRPJ93 and the premium 45 mm Sumo SPB375. All three are rated to 200 m for diving and share an ocean-blue PADI design, but they suit different buyers: choose the SRPK01 for a bracelet, day-date display and classic Turtle case; the SRPJ93 for a slightly smaller, thinner Samurai on silicone; and the SPB375 when a longer power reserve and more refined, coated Sumo case justify a price near twice that of the other two.
What the PADI “Great Blue” editions have in common
These are special editions created through Seiko’s partnership with PADI, the Professional Association of Diving Instructors. Their common visual language is a graduated or deep-blue ocean theme, PADI branding and a unidirectional elapsed-time bezel intended for dive timing. Each has a screw-down crown and caseback, sapphire crystal and a stated 200 m water-resistance rating described as suitable for scuba diving.
The rating is the same across the trio. The premium SPB375 therefore does not buy a higher stated depth rating; its advantages are primarily the Sumo case construction, Super-Hard coating, ceramic bezel insert and longer-running movement.
At a glance: the three watches
| Model | Case and wear dimensions | Movement and reserve | Calendar | Crystal and bezel | Strap or bracelet | Water resistance | Published price reference |
|---|---|---|---|---|---|---|---|
| SRPK01 King Turtle | 45 mm diameter; 13.22 mm thick; 47.7 mm long; 22 mm lugs | 4R36 automatic, 21,600 vph, 24 jewels; approximately 41 hours | Magnified day/date | Sapphire with inner anti-reflective coating; blue ceramic unidirectional bezel | Stainless-steel bracelet with folding clasp, secure lock and diver’s extension | 200 m / 660 ft, suitable for scuba diving | EUR 660 launch retail price (Monochrome, 2023); Seiko USA lists $650 |
| SRPJ93 King Samurai | 43.8 mm diameter; 12.8 mm thick; 48.7 mm lug-to-lug; 22 mm lugs | 4R35 automatic with manual winding and stop-seconds; 23 jewels; approximately 41 hours | Date only | Sapphire with magnifier and inner anti-reflective coating; ceramic-display bezel | Blue silicone band with PADI markings | 200 m / 660 ft diver’s water resistance | EUR 640 launch retail price (Monochrome, 2023) |
| SPB375 Sumo | 45 mm diameter; 12.9 mm thick | 6R35 automatic with hacking seconds and quick-set date; approximately 70 hours | Date | Sapphire; unidirectional ceramic bezel insert | Super-Hard-coated stainless-steel bracelet with folding clasp and wetsuit extension | 200 m | EUR 1,250 launch retail price (Monochrome, 2023) |
Launch prices are historical references, not current offers. Prices, stock and regional availability change, and the official SRPK01 page displayed a “Notify me when in stock” status when accessed on October 1, 2026.
#1 Best Overall
- 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
- LUMIBRITE DISPLAY: this men's dive watch features a highly-legible display with LumiBrite hands and markers
- STAINLESS STEEL: features a durable stainless steel watch case and bracelet, unique case shape resembling teeth, and PADI red and blue colors on its elapsed timing bezel
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men's watch keeps precise time
SRPK01: the bracelet King Turtle
What you get
The SRPK01 is the most traditional-looking option in the group. Its 45 mm Turtle case measures 13.22 mm thick and 47.7 mm long, with the crown positioned at 4 o’clock. The 4R36 automatic movement runs at 21,600 vibrations per hour, contains 24 jewels and provides approximately 41 hours of reserve. It also supports manual winding.
Its magnified day-date display is the practical distinction from the other two models: you get both the day and the date rather than a date alone. Seiko specifies a sapphire crystal with inner anti-reflective coating, a blue ceramic unidirectional bezel, LumiBrite hands and markers, and a tri-fold bracelet clasp with a diver’s extension.
Rank #2
- STAINLESS STEEL CASE built to endure with style, making this watch your perfect daily companion
- AUTOMATIC MOVEMENT for seamless precision in every tick of this watch
- SCRATCH-RESISTANT CRYSTAL to maintain a pristine look even with daily wear and tear on your watch
- LUMINESCENT HANDS for effortless readability in low-light conditions, ensuring you never miss a moment with this watch
- WATER RESISTANT DESIGN ensuring your watch is ready for any adventure, rain or shine
Who should choose it
- Choose it if a steel bracelet is your starting point and you want day-date functionality.
- Its 45 mm diameter and 13.22 mm thickness create the largest stated physical footprint of the two 4R-powered models.
- It is a genuine ISO-oriented scuba-diver specification from Seiko’s listing: 200 m water resistance, screw-down components and dive-timing bezel.
SRPJ93: the slimmer-feeling King Samurai option
What changes from the Turtle
The SRPJ93 uses the angular King Samurai case, measuring 43.8 mm across and 12.8 mm thick, with a 48.7 mm lug-to-lug length. Those dimensions make it narrower in diameter and thinner than the SRPK01, although its stated lug-to-lug measurement is longer. The case has a ceramic-display bezel and a sapphire crystal with both a magnifier and inner anti-reflective coating.
Its 4R35 automatic movement offers manual winding, stop-seconds and approximately 41 hours of reserve. The display is date-only. A blue silicone band, rather than a steel bracelet, completes the package and carries white PADI markings.
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- 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
- LUMIBRITE DISPLAY: this men's dive watch features a highly-legible display with LumiBrite hands and markers
- STAINLESS STEEL: this diving watch for men features a stainless steel watch case and bracelet, a uni-directional rotating elapsed timing bezel, and a bold blue dial evoking signature PADI colors
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men's watch keeps precise time
Who should choose it
- Choose it if you prefer the Samurai’s sharper case profile and a silicone strap.
- It is the smallest by diameter and tied with the SPB375 for the lowest stated thickness, but its 48.7 mm lug-to-lug span still matters on shorter wrists.
- Its specifications retain the 200 m diver’s rating, sapphire crystal and ceramic bezel treatment while keeping the launch price slightly below the SRPK01’s.
SPB375: what the Sumo premium buys
The movement advantage
The SPB375 uses Seiko’s 6R35 automatic calibre, with hacking seconds and a quick-set date. Its approximately 70-hour power reserve is about 29 hours longer than the roughly 41-hour reserve quoted for the SRPK01 and SRPJ93. That extra reserve is useful when the watch is set down for a weekend: it is more likely to keep running without being rewound or reset.
The case and bracelet advantage
The 45 mm Sumo is 12.9 mm high and uses a Super-Hard-coated stainless-steel case and bracelet. It adds a sapphire crystal, screw-down crown and caseback, a unidirectional ceramic bezel insert and a folding clasp with wetsuit extension. The stated water resistance remains 200 m.
Rank #4
- PADI SPECIAL EDITION: Men's Prospex Sea diver watch features PADI Special Edition details and a durable stainless-steel case.
- AUTOMATIC MOVEMENT: Seiko 4R35 automatic movement with manual winding, 23 jewels, stop-second function, date display, and approximately 41-hour power reserve.
- 200M DIVER'S WATCH: 200m/660ft diver's water resistance, screw-down crown, and screw case back support underwater use.
- SAPPHIRE CRYSTAL: Sapphire crystal with magnifier and inner anti-reflective coating provides enhanced clarity and scratch resistance.
- CERAMIC BEZEL & SILICONE BAND: Stainless-steel bezel with ceramic display and unidirectional rotation pairs with a flexible silicone band.
Is it worth roughly twice as much?
On the published launch figures, the SPB375’s EUR 1,250 price was close to twice the EUR 640–660 launch prices of the King Samurai and King Turtle. That premium is not payment for a deeper rating or a proven accuracy improvement; the documented upgrades are the Sumo’s more elaborate case treatment, Super-Hard coating, ceramic bezel insert, bracelet and the 6R35’s substantially longer reserve. It is easiest to justify if those construction and movement differences matter more to you than the lowest entry price.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose for your wrist and routine
Start with case dimensions
- Most compact diameter: SRPJ93 at 43.8 mm.
- Largest diameter: SRPK01 and SPB375 at 45 mm.
- Thinnest stated case: SRPJ93 at 12.8 mm, followed by SPB375 at 12.9 mm and SRPK01 at 13.22 mm.
- Longest stated measurement: SRPJ93 at 48.7 mm lug-to-lug; SRPK01 is listed at 47.7 mm.
Diameter alone does not predict how a diver wears. Compare the lug-to-lug span, thickness and the strap or bracelet when judging whether a large case will overhang your wrist. The specifications establish dimensions, not personal comfort, so trying the watch on remains the reliable check.
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- PADI SPECIAL EDITION: Men's Prospex Sea diver featuring a PADI Special Edition design with a stainless-steel case and ceramic bezel display.
- AUTOMATIC MOVEMENT: Seiko 4R36 automatic movement offers manual winding, 24 jewels, day/date display, stop-second function, and approximately 41 hours of power reserve.
- 200M DIVER'S WATER RESISTANCE: Rated to 200 meters / 660 feet for diving, with a screw-down crown and screw case back.
- SAPPHIRE CRYSTAL: Sapphire crystal with magnifier and inner anti-reflective coating provides durable dial protection and improved readability.
- DIVER-READY FEATURES: 45mm stainless-steel case, unidirectional rotating bezel, LumiBrite hands, indexes and bezel, plus a secure three-fold clasp with extender.
Then choose the contact surface
- Steel bracelet: SRPK01 or SPB375, both with a clasp and diver’s extension.
- Silicone: SRPJ93, the lightest-material choice in the trio on paper and the only one supplied on a silicone band.
Finally choose the movement behavior
- Pick the SRPK01 if day-date is important.
- Pick the SRPJ93 if date-only simplicity and the 4R35’s stop-seconds and manual winding meet your needs.
- Pick the SPB375 if a roughly 70-hour reserve is worth the additional cost and the date-only Sumo layout is acceptable.
Are the SRPK01, SRPJ93 and SPB375 real dive watches?
They are specified as dive watches, not merely dive-styled sports watches. Seiko lists 200 m water resistance for each model, screw-down crown and caseback construction, a unidirectional elapsed-time bezel and luminous dive-time indications. The SRPK01 listing explicitly describes the watch as following ISO standards for scuba diving and being suitable for scuba diving.
Those specifications do not replace basic dive-watch practice: water resistance is not permanent, seals age, and a watch should be inspected and pressure-tested according to the manufacturer’s guidance before serious use. The available information establishes design and ratings, not independent real-world dive testing.
Bottom line: which Great Blue should you buy?
Buy the SRPK01 for the most conventional package: Turtle styling, steel bracelet, day-date display and a 200 m scuba-diver specification. Buy the SRPJ93 for the King Samurai shape, slightly smaller diameter, silicone strap and the lowest launch price. Choose the SPB375 when its Sumo case finishing, Super-Hard coating, ceramic bezel and approximately 70-hour reserve justify spending around twice as much; its water-resistance rating is still 200 m, not higher.
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