Monochrome Watches
An online magazine dedicated to fine watches

The Seiko Prospex PADI SRPK01, SRPJ93 & SPB375 Are Ready To Take The Plunge

Three new special editions based on the ever-popular Turtle, Samurai and Sumo models.

| By Robin Nooy | 6 min read |

In the world of aquatic watchmaking, few (if any) can offer such an extensive and comprehensive collection of diving-oriented watches as Seiko. Since the mid-1960s, the Japanese powerhouse has been one of the most prolific manufacturers when it comes to diving watches. Icons like the 62MAS, the SKX, the Turtle, the Samurai, Sumo, Tuna and Shogun… we can go on and on, really. Working together with PADI, the premier diving instruction organization in the world, Seiko releases a series of PADI special editions pretty much every year. Designated as the Great Blue models, this year we get the King Turtle SPRK01, King Samurai SPBJ93 & Sumo SPB375!

Professional Association of Diving Instructors

Simply known as PADI, the Professional Association of Diving Instructors is a world-leading and one of the most trusted scuba diving organizations (The other being Scuba Schools International or SSI). Since 1966, PADI has pretty much been a standard format for learning how to dive correctly, ranging from entry-level courses to relatively advanced certifications. With over 6,300 diving centres spread around the globe, they have issued over 27 million scuba certifications. The partnership with Seiko started back in 2016 and has resulted in regular new models being introduced with various oceanic themes. The series of special editions have been quite popular, offering cool vibes with solid specs and a decent price tag. This year’s editions are based on the ever-popular (King) Turtle, (King) Samurai and Sumo sub-collections.

Ad – Scroll to continue with article

The PADI “Great Blue” king Turtle SRPK01

First up, is the new PADI “Great Blue” King Turtle SPRK01. This one uses the sharper knurled bezel, the sapphire crystal and the ceramic bezel insert from the previous King Turtle models to set it apart from the regular Turtle. We’ve explained what differentiates the two when the first King Turtle was launched, back in 2016. What hasn’t changed though, is the barrel-shaped 45mm by 13.2mm stainless steel brushed and polished exterior. The bezel still rotates one way only and is fitted with a deep blue insert with a light blue and silver/grey segmented diving scale. It also retains the 200m water resistance and the crown at 4′, which has always been a very distinctive design element of the Turtle.

The dial of this “Great Blue” edition is reminiscent of the ocean’s surface seen from just below it. You can see the light penetrating it and gradually getting dimmer and darker. The top half also shows wave-like ripples, a cool touch that adds character and depth to it. The applied markers and hands are finished with LumiBrite of course, and the sapphire crystal has a loupe over the day and date window. Inside ticks the familiar 4R36 automatic movement, running at a frequency of 21,600vph and offering a power reserve of 41 hours. The back of the case is solid, so you don’t see the movement at work.

Worn on a stainless steel bracelet with a folding clasp and diver’s extension, the Seiko Prospex PADI “Great Blue” King Turtle SRPK01 retails for EUR 660. And with that, despite the upgrades over the regular Turtle, this one still offers very good value for money.

Quick Facts – 45mm diameter x 13.2mm height x 47.7mm L2L – stainless steel, sapphire crystal with magnifier, unidirectional bezel with ceramic insert – screw-down crown and caseback – 200m water-resistant – Calibre 4R36, in-house, automatic, 3Hz frequency, 41h power reserve – HMS with day-date – steel bracelet with folding clasp and diver’s extension – special edition – EUR 660

The PADI “Great Blue” king samurai SRPJ93

The second in the series is the Seiko Prospex PADI “Great Blue King Samurai SRPJ93. The recipe is similar to the King Turtle we’ve just discussed, except for the fact it’s based on the much more angular King Turtle. This again is set apart from the regular Samurai by its sapphire crystal with cyclops and the ceramic bezel insert. For the rest, you still get that rugged-looking square-ish steel case with a unidirectional rotating bezel and a sturdy crown with a set of crown guards at 3′.

Just like the other two, it features a blue dial that gets darker towards the bottom. The hour indices are now rectangular, with the exception of the ones at 6, 9 and 12 o’clock. Another shared element between the three is the blue minute hands, tying in with the blue on the diving scale of the ceramic bezel insert. The King Samurai shows only the date but does come with a magnifier on top of the sapphire crystal.

Using the Calibre 4R35, once again covered by a solid caseback, there are no surprises on the inside either. It’s all the usual, but admittedly pretty solid stuff. The 4R35 automatic movement beats at the same 3Hz frequency as the King Turtle’s 4R36 and offers the same 41 hours of running time. What does set it apart in this trio is the deep blue rubber strap with pin buckle, and printed PADI markings in white. This one has a price of EUR 640, making it the most affordable of the series, but only just.

Quick Facts – 43.8mm diameter x 12.8mm height x 48.7mm L2L – stainless steel, sapphire crystal with magnifier, unidirectional bezel with ceramic insert – screw-down crown and caseback – 200m water-resistant – Calibre 4R35, in-house, automatic, 3Hz frequency, 41h power reserve – HMS with date – deep blue rubber strap with printed PADI markings in white – special edition – EUR 640

THE PADI “Great Blue” sumo SPB375

Rounding out the trio is the Seiko Prospex PADI “Great Blue” Sumo SPB375, the top-tier model of these new releases. Based on the beefy Sumo that was first introduced in 2007, this one falls in line with the other two. We once again have a blue dial with that sub-surface rippled pattern in blue, again darkening from top to bottom. It also has a ceramic bezel insert with a two-tone diving scale and blue minute hands. The roundels for the hour markers, as well as the central hands, have a LumiBrite insert. So far, nothing out of the ordinary.

What does set the Sumo SPB375 apart from the King Turtle and King Samurai, is the construction of the case and the selected movement. This was updated last year, with a case that has been given more attention to detail and finishing compared to its more affordable siblings. The large and hefty case has always been fitted with a sapphire crystal and has a crown at 4′ to not dig into the wrist too much. Retouched in 2019, and then again in 2022, this new Sumo SPB375 still measures a sizeable 45mm in diameter and 12.9mm in height. Since last year though, it has been given a Super-Hard coating to make it more scratch-resistant. Also new since the SPB321J1 and SPB323J1 is the ceramic bezel insert.

The Sumo always relied on the Calibre 6R35 automatic, so nothing has changed on the inside since its release. The very welcome 70 hours of power reserve is perhaps the greatest trump card compared to the other two new PADI models, but it does come with a significantly higher price. Priced at EUR 1,250, it comes on a Super-Hard coated stainless steel three-link bracelet with a folding clasp that also incorporates a wetsuit extension. Yes, this one is roughly twice as expensive as the other two, but you also get quite a bit more in return.

Quick Facts – 45mm diameter x 12.9mm height – stainless steel, sapphire crystal, unidirectional bezel with ceramic insert – screw-down crown and caseback – 200m water-resistant – Calibre 6R35, in-house, automatic, 3Hz frequency, 70h power reserve – hours, minutes, hacking seconds and quick-set date – stainless steel bracelet with Super-Hard coating and new folding clasp with wetsuit extension – EUR 1,250

For more information, please visit

7 responses

  1. The PADI series should be more technical in their design, and more closely inspired by instruments. Colourful? Why not (as in early Pepsi versions), but without the artsy dials.

  2. Your Padi presentation “ Professional Association of Diving Instructors is the world’s leading and most trusted scuba diving organization” is misleading if not wrong.There are 2 diving associations. PADI & SSI.!!! and both PADI and SSI offer world-class diving training around the world. They both maintain high standards of practice across the globe. So, please do your homework carefully next time.

  3. Hi Spiros,

    Thank you for the comment. I made some changes to the paragprah on PADI.

    All the best, Robin.

  4. The Sumo did not always have sapphire. The first models had hardlex. Similarly, the first models had the 6r15 movement, not the 6r35 movement.

  5. It is said that Seiko has QA problems. Well, in what is look like sample send to reviewers they should be super vigilant about quality, yet Sumo has misaligned either 12 hour mark, or inner ring with minute marks, because these does not line up. Lol.

  6. Padi King Samurai: Hour indices at 7 and 8 are not correctly aligned 😉

Leave a Reply