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The Omega Seamaster Diver 300M Summer Blue, reference 210.30.42.20.03.003, is the 42 mm stainless-steel version of OMEGA’s Summer Blue Diver 300M, released in 2023 to mark 75 years of the Seamaster line. It houses the automatic OMEGA Calibre 8800 and is listed with a steel bracelet. This guide covers what OMEGA’s official launch announcement, model page and video confirm, and it flags what those sources cannot tell you. It does not include wrist-time impressions, so comfort, fit and finish are left for you to check in person.
Which reference this is
The reference that matters is 210.30.42.20.03.003. OMEGA’s Japan-localized model page identifies it as a 42 mm stainless-steel Seamaster Diver 300M with the Co-Axial Master Chronometer label and the Calibre 8800 movement, and it is the steel-bracelet configuration of the Summer Blue model. Other Summer Blue references exist in the same family, so the suffix is the only reliable way to match a listing to this watch. Before buying, confirm that the reference on the paperwork, the box or the seller’s listing ends in .03.003. The official page is available at OMEGA Japan, Seamaster Diver 300M, ref. 210.30.42.20.03.003.
The 75th anniversary collection behind it
OMEGA introduced its Summer Blue Seamaster collection in June 2023 to celebrate 75 years of the Seamaster. The collection comprised 11 watches across seven models. According to OMEGA’s launch announcement, the shared Summer Blue colour was meant to reflect the water resistance of each Seamaster, and it was applied to different degrees across the range. The gradient dial on this reference is therefore part of a collection-wide design language rather than a standalone blue variant. The launch material is available at OMEGA Press, Seamaster: Precision at Every Level.
Dial, bezel and case
OMEGA’s product video describes a ceramic dial in the Summer Blue tone, finished with a gradient varnish and a wave pattern. The bezel’s diving scale is picked out in the same bold blue. OMEGA presents the model under the title “Seamaster in Summer Blue: Diver 300M. 300 metres.” The case is 42 mm in stainless steel, a size OMEGA lists on its model page.
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- Omega Seamaster Automatic Black Dial Men's Watch 210.32.42.20.01.001
Specifications at a glance
The table below separates the values OMEGA publishes from the details its sources leave out. Where a figure is not stated, the cell says so rather than estimating.
| Attribute | Listed value | Source and date |
|---|---|---|
| Reference | 210.30.42.20.03.003 | OMEGA Japan model page, accessed 2026 |
| Case | 42 mm, stainless steel | OMEGA Japan model page, accessed 2026 |
| Movement | Automatic OMEGA Calibre 8800, Co-Axial escapement | OMEGA Japan model page, accessed 2026 |
| Certification | Master Chronometer | OMEGA Japan model page, accessed 2026 |
| Power reserve | 55 hours | OMEGA Japan model page, accessed 2026 |
| Frequency | 3.5 Hz (25,200 beats per hour) | OMEGA Japan model page, accessed 2026 |
| Magnetic resistance | More than 15,000 gauss | OMEGA Japan model page, accessed 2026 |
| Water resistance | 300 metres (Diver 300M) | OMEGA video title and description, 2023 |
| Case thickness, lug width, weight | Not stated | Not stated in the OMEGA sources reviewed |
| Price | Not stated as a single figure; the Japan page shows a yen price for that market only | OMEGA Japan model page, accessed 2026 |
What the movement figures mean in practice
The Calibre 8800 is an automatic movement, so it winds from the wearer’s motion and needs no daily winding when worn regularly. The 55-hour power reserve describes how long it runs without being worn; a watch left in a drawer will stop sooner than that if it is not wound. The 3.5 Hz rate is the balance’s oscillation frequency. The Co-Axial escapement is OMEGA’s own design, and the Master Chronometer label is the one the model page lists for this reference. The 15,000-gauss figure is the magnetic resistance OMEGA publishes for the model; it describes resistance to magnetic fields and does not guarantee accuracy in every environment.
Rank #2
- Omega Seamaster Automatic Chronometer Black Dial Men's Watch 210.30.42.20.01.001
Straps and bracelet
- Steel bracelet: the configuration this reference is listed with on OMEGA’s model page.
- Blue rubber strap: OMEGA’s video shows a blue rubber-strap option for the 42 mm Summer Blue Diver 300M. That strap is not part of reference 210.30.42.20.03.003, so a listing for the rubber version should carry its own reference.
A third-party strap should not be assumed to fit. Check the lug width and the strap’s compatibility with this specific reference before ordering.
What the official sources cannot tell you
OMEGA’s materials describe construction, specifications and design intent. They do not evaluate how the watch performs on a wrist. The following points need to be checked in person:
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- Model 210.90.42.20.01.001
- How the 42 mm case sits on your wrist, including lug overhang and overall thickness
- Bracelet comfort, link removal and the feel of the clasp and its micro-adjustment
- How the gradient dial reads in daylight, indoors and in low light
- Bezel action: click precision and resistance
- Lume strength and duration on the hands and indices
- Overall weight and how it balances on the wrist over a full day
How to check it in person
- Confirm the reference ends in .03.003 against the paperwork or listing before you visit a boutique or dealer.
- Ask for the bracelet version so you can try the steel configuration directly.
- Wear it for at least 20 to 30 minutes and move your wrist through typical positions, checking for pressure points and clasp irritation.
- View the dial in natural light, under indoor lighting and in a dim room to judge legibility and the gradient.
- Rotate the bezel and note any play or uneven clicks.
Price, availability and buying checks
No single current price for this reference was established across markets. The Japan model page shows a yen price that applies to that market only, and it should not be used as a global figure. Prices, stock and warranty terms vary by region and seller, so confirm them at the point of purchase.
- Buy from an OMEGA boutique, an official OMEGA retailer or a seller you can verify.
- Check the exact reference and whether the bracelet or the rubber strap is included.
- For a pre-owned or unworn-stock watch, ask for the seller’s written warranty terms and proof of origin.
- Compare the final price including tax and duties in your own currency.
OMEGA’s launch video is available at OMEGA, Seamaster in Summer Blue: Diver 300M. 300 metres.
Rank #4
- Model 212.30.44.52.01.001
The Bottom Line
Shortlist reference 210.30.42.20.03.003 if you want a 300-metre-rated OMEGA dive watch with a Master Chronometer-labelled Calibre 8800 movement, a 42 mm steel case and the Summer Blue livery from the 2023 anniversary collection. Hold the purchase until you have worn it on a bracelet, because the case size, bracelet comfort and dial legibility are the points the official sources do not settle.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
