OMEGA · Seamaster Diver 300M
OMEGA Seamaster Diver 300M 210.30.42.20.01.001: specifications and checks
OMEGA's actual dive watch: 300 metres, calibre 8800 running at 3.5 Hz with 55 hours. A higher beat rate and a shorter reserve than the Aqua Terra, and a different movement family entirely.
Reference 210.30.42.20.01.001 · specifications read from the manufacturer on 2026-09-23 · listed as current
Specifications
As published by OMEGA. A field the manufacturer does not state is left out rather than filled in.
- Case
- Steel, 42 mm
- Diameter
- 42 mm
- Thickness
- 13.56 mm
- Lug width
- 20 mm
- Lug to lug
- 49.9 mm
- Water resistance
- 30 bar (300 metres / 1,000 feet)
- Crystal
- Domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides
- Dial
- Black
- Bracelet
- Steel
- Clasp
- Foldover clasp with comfort setting and diver extension
Movement
- Calibre
- Calibre OMEGA 8800
- Type
- Self-winding movement with Co-Axial escapement, automatic winding in both directions
- Power reserve
- 55 hours
- Frequency
- 3.5 Hz
- Certification
- Master Chronometer, approved by METAS
- Notes
- Resistant to magnetic fields reaching 15,000 gauss. Free sprung-balance with silicon balance spring. Rhodium plated finish with Geneva waves in arabesque. Total product weight approximately 194 g.
What to check before you buy
- Confirm the calibre is the 8800 and not the 8900 used in the Aqua Terra. They are different movements with different reserves, and the 8800 has no time zone function to demonstrate.
- Check the crown screws down properly. At 300 metres this is a genuine dive rating and the crown is a primary seal, so any binding or reluctance to seat matters.
- Look at the anti-reflective coating on the inner crystal face as well as the outer. Interior hazing cannot be polished and means the crystal is due for replacement.
- Run it for two full days. At 3.5 Hz with 55 hours of reserve, this movement gives you less margin than the 60- and 70-hour calibres, so a watch left off the wrist over a weekend will stop.
- Verify the 42mm case sits acceptably on the buyer's wrist before shipping. It is a large dive watch, and dive cases wear larger than their diameter suggests.
Three hundred metres, and a different movement
This is the reference people mean when they say Seamaster without qualifying it. 30 bar — 300 metres — makes it a real dive watch, unlike the Aqua Terra at 150 or the Moonwatch at 50.
The movement is also different, and that catches people out. This carries the calibre 8800, not the 8900. Both are Co-Axial Master Chronometers approved by METAS with resistance to 15,000 gauss, but they are separate movements with separate specifications.
Faster beat, shorter reserve
The 8800 runs at 3.5 Hz with 55 hours of power reserve. The Aqua Terra's 8900 runs slower and holds 60 hours; the Moonwatch's 3861 holds 50 at 3 Hz.
Two practical consequences for a dealer.
First, do not quote one calibre's figures for another. The three OMEGA references on this site have three different reserves, and a listing that says "60 hours" on this watch is simply wrong.
Second, the shorter reserve changes ownership. Fifty-five hours means a watch taken off on Friday evening will very likely be stopped by Sunday, where a 70-hour movement would still be running. That is worth mentioning to a buyer comparing it against a Rolex, most of which hold seventy.
The 8800 has nothing extra to demonstrate
The 8900 in the Aqua Terra carries a time zone function with an independently adjustable hour hand. The 8800 does not.
That is not a shortcoming — it is a simpler movement in a tougher case — but it does mean your inspection is shorter. There is no complication to exercise here, so attention goes to the case, the crown and the crystal instead.
Coating on both faces, again
As on the Aqua Terra, the crystal is domed sapphire with anti-reflective treatment on both sides. The inner coating is the one that matters, because it cannot be reached.
Hold the watch with a light behind you and look through the crystal at a shallow angle. Uneven bloom or haze from the inside means a crystal replacement, not a polish — and it is invisible in almost every photograph a seller will send.
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Sources
Not affiliated with OMEGA. Specifications are read from the manufacturer's own published documentation on the date shown and may change; the manufacturer's current documentation governs.