Seiko SRPA21 Review – Prospex X Padi Automatic Watch Guide

Seiko SRPA21 Review – Prospex X Padi Automatic Watch Guide

Seiko is perhaps most known and appreciated for its automatic dive- and tool watches. Seiko makes some of the best automatic watches in the world within its price range. It is particularly its dive watches that are popular among watch enthusiasts. The watches offer extremely great value for money. One of these watches is the Seiko Prosper X Padi Automatic watch SRPA21.

This watch is a serious dive-and-tool watch from Seiko that offers all of the things mentioned, and much more.

But is the SRPA21 really as good as people say it is?

 Seiko SRPA21 Review

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The Seiko SRPA21 is a special edition timepiece Mae to celebrate Seiko’s association with the Professional Association of Diving Instructors, also known as PADI. 

This watch is large, it is sporty, it is robust, but has a unique and interesting colorway. Its bright and bold colors are what make an already appreciated and loved watch even more special. 

The SRPA21 is almost identical to the standard version of this Turtle, reference SRP775. It has the exact same dimensions, weight, and movement.

What collectors and enthusiasts especially love about this watch is the fact that you can enjoy the vintage-inspired aesthetics of a dive watch, but do so in a modern, durable, and reliable shape and form, without having to worry about breaking it (or that something will break). This watch was released in 2016 as a special edition, but despite being a modern timepiece, it looks vintage.

PADI is one of the most trusted scuba diving training organizations, and with that said, a partnership between this organization and Seiko with its professional dive watch makes sense. If the watch is approved by them –  the experts, it will be good enough for anyone.

Let’s look at this watch more in detail.

Seiko SRPA21 Review - Prospex X Padi Automatic Watch Guide

Photo: Professionalwatches

Seiko SRPA21 case

The Seiko SRPA21 has a 45mm cushion-style stainless steel case. This case shape is what collectors today call a”turtle”.

The history of the turtle goes all the way back to 1977 when Seiko released the first turtle. This watch is very similar to the SRPA21. It’s affordable, it’s durable, it’s good looking, and it’s long-lasting. What more can you ask for?

The case itself is familiar to many other Seiko dive watches, so this is nothing new. It has drilled holes at the lugs which allow for easy replacement and changing of the spring bar. In terms of practicality, the drilled lugs are worth a lot. In terms of aesthetics, they do split onions.

Furthermore, the top of the case is brushed in a circular pattern. This adds to the tool-like finish and looks of the watch. The sides of the case are polished which creates a nice contrast.

45mm is on the larger size, but thanks to the relatively short lugs, it wears smaller than what is indicated on paper. The case has the classic crown position at 4 o’clock, discretely integrated into the case. The crown is 7 mm in diameter. The positioning of the crown provides more comfort than the traditional 3 o’clock position as it prevents the crown from digging into the wrist. It is interesting to see that Seiko has not made a crown guard, but rather integrated the crown into the case which thus protects it. Crown guards simply weren’t necessary for this model, and the case did the protection very well. The crown is of course screw-down. 

The case is also equipped with a unidirectional rotating bezel, seeing this is a dive watch. For improved legibility, it has a luminous pip at 12:00. The colorful aluminum insert contributes to its playful and appealing aesthetics, with red color for the first  20 minutes and then the rest is blue. The bezel also has clear and easy-to-read indicators. A complaint that some people have reported is that some examples do not have aligned bezels. This means that it will be slightly mispositioned. This can be fixed and covered under warranty, but at this price, we feel that it is within what you would expect for a watch in this price range.

According to Seiko, the case has a magnetic resistance of 4,800 A/m. 

The watch is fitted with Seiko’s proprietary Hardex crystal-like so many of Seiko’s other watches. At this price point, sapphire crystal isn’t really used extensively due to its high cost. Plus, the Hardlex crystal has proven to be much more durable and scratch-resistant than standard mineral glass.

The case back is a solid etched and embossed screw-down case back for optimum resistance and protection against water and leakage.

As the diving watch it is, it has a water resistance of 200 meters. This is enough to be worn when swimming and even diving. Furthermore, the watch fulfills the ISO 6425 standards for dive watches.

Seiko SRPA21 movement

The Seiko Prospex Padi SRPA21 is powered by the automatic and mechanical 4R36 movement. This is a 24-jewel movement with a 41-hour power reserve when fully wound. The movement displays hours, minutes, seconds, day, and date.

This movement is a self-winding caliber with manual-winding capacity and hacking seconds. It beats at 3Hz (21,600 vph).

This movement has proven to be a workhorse. This movement was introduced in 2011 and is both extremely reliable and precise. Plus, it is also durable and robust. Just what you expect and need from a movement that is fitted inside a sporty dive watch.

Seiko SRPA21 Review - Prospex X Padi Automatic Watch Guide

Seiko SRPA21 dial

Without using too many fuzz words, we can say that the dial of the SRPA21 is simply beautiful. The dial has a stunning sunburst dial in blue which reflects the light beautifully and gives a rich depth to it. At 3 o’clock, we have Seiko’s iconic day and date window which of course serves a practical purpose.

Moving on to the markers, which are painted instead of applied. The markers are generously treated with Seiko’s Lumibrite which means the watch glows strong and offers great legibility in low-lit conditions. On the outer part of the dial, there is a ”ramp” (chapter ring) with painted white minute markers and red 5-minute markers. The small red details go really well with the red on the bezel and also look great against the blue.

With that said, the blue and the red colorway has led it to be nicknamed ”Pepsi”.

Lastly, the minute hand is also made in red to further go with the theme of the watch. The minute hand is shaped like a triangle against the blue background providing great legibility.

The Seiko Prospex SRPA21 stays true to its predecessors and has an almost identical dial layout.

On the dial, we also have some printing. Firstly, there is the Seiko logo at the top. Then beneath that is the Prospex logo. Below the center, of the hands is in turn the PADI logo (remember, this watch is a PADI special edition). Right beneath that, you have the automatic printing and then the depth rating. Yes, the watch has quite a bit of printing on the dial, but in one way, it feels like it is not too much. Yes, the dial could have been made less cluttered, but in a sense, we wouldn’t want to remove anything as each piece of text or logo has an important place and stands for something.

Interesting to note about this watch is the fact that the iconic “X” Prospex logo that is printed on its dial is very special. It is the first time for Seiko to use this logo in an affordable timepiece. The Prospex logo reminds us that it is a watch with professional specifications.

Seiko SRPA21 bracelet

Unlike the standard Pepsi SRP779 which is delivered on a black rubber strap, this watch comes fitted on a stainless steel bracelet with a double locking fold-over push-button clasp with a divers extension.

The watch weighs a total of grams with the metal bracelet. The good news is that thanks to the lug holes, you can easily and effortlessly switch to a rubber strap or a nato strap in case you find the metal bracelet too clumsy or bulky. A lot of people choose to fit their watch with the rubber strap for comfort and looks.

The bracelet is 22 mm in width at the lugs and tapers to 20 mm at the clasp. 


The Seiko Turtle SRPA21 Prospex X Padi is really an impressive tool and dive watch that offers incredible value for money. It is qualitative, robust, solid, powered by automatic movement, and much more. The watch also has an interesting and appealing history, as well as a great visual appearance.

You shouldn’t expect Rolex quality or a Patek Philippe finish, but looking at what you get and having the price in mind, it is undeniably one of the greatest dive watches for the money on the market.

Overall, this is a fun and great watch that you should definitely consider buying.

The Seiko SRPA21 is available to order on Amazon.

Seiko SRPA21 Review - Prospex X Padi Automatic Watch Guide


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