“DOXA Sea Emerald” refers to two watches, not one: the SUB 300T Sea Emerald (reference 840.10.131.10) and the SUB 300 Sea Emerald (reference 821.10.131.10). Both have 42.5 mm steel cases, a green sunray dial, date, and beads-of-rice bracelet configuration. The main choice is between the SUB 300T’s manufacturer-rated 1,200 m water resistance and helium release valve, and the SUB 300’s 300 m rating and explicitly stated COSC-certified movement.
Which DOXA Sea Emerald is which?
DOXA applies the Sea Emerald colorway to two models in its SUB line. Check the model name or reference number when comparing listings, buying a watch, or looking for a strap: the specifications and prices are not interchangeable.
- SUB 300T Sea Emerald: reference 840.10.131.10. DOXA’s US product listing showed USD 2,190 when checked on October 8, 2026. See DOXA’s SUB 300T listing.
- SUB 300 Sea Emerald: reference 821.10.131.10. DOXA’s US product listing showed USD 2,890 when checked on October 8, 2026. See DOXA’s SUB 300 listing.
These are displayed official US prices, not guaranteed transaction prices. Prices, stock, taxes, shipping, and promotions can change; check the live regional listing before ordering. DOXA’s UK SUB 300T listing showed GBP 1,890 on the same date, illustrating that price varies by market. Check DOXA’s UK SUB 300T listing.
SUB 300T vs. SUB 300: specifications
The figures below are specifications published by DOXA, not independent test results.
#1 Best Overall
- NH35A Movement: This tactical frog watch V2 Orange is powered by the 24 Jewels NH35A self-winding movement, Assembled in Japan. Delicate and accurate.Power reserve can last for 41 hours.
- Cool Automatic Watch: Scratch resistant sapphire crystal glass with anti-reflective coating on inner surface; Stainless steel bracelet is adjustable by removing or adding links and fold over clasp with safety. A must have tactical frog watch for collection.
- Diving Watches: Double layer bezel design. Screw down lock for water tight seal and uni-directional outer stainless steel bezel to tell you "under" time easilly. Tactical frog mechanical watch is water resistant to 200M(20ATM). Suitable for professional marine activities, swimming, water sports and daily wearing.
- Luminated Watch: Green Luminious hands, scales and hour markers are featuring Swiss C3 material, which can last for at least 5 hours in dark and is able to quickly absorb and store light energy in a bright environment.
- Fashionable Style: The stylish outlook and vivid colored dial enhanced the sport and dynamic feel. A fashionable watch present for men, a must have for watch collection.
| Specification | SUB 300T Sea Emerald | SUB 300 Sea Emerald |
|---|---|---|
| Reference | 840.10.131.10 | 821.10.131.10 |
| Movement | Swiss automatic, self-winding; 38-hour power reserve; 28,800 vph. COSC certification is not claimed on the cited product page. | Swiss automatic, self-winding; COSC certified; 38-hour power reserve; 28,800 vph. |
| Case | 316L stainless steel; 42.50 mm diameter × 44.50 mm; 13.65 mm thick | 316L stainless steel; 42.50 mm diameter × 45.00 mm; 13.40 mm thick |
| Water resistance | 120 ATM / 1,200 m / 3,937 ft | 30 ATM / 300 m / 984 ft |
| Bezel scale | Unidirectional, marked in feet | Unidirectional, marked in meters |
| Other listed features | Date; sapphire crystal; sunray dial; helium release valve | Date; sapphire crystal; sunray dial |
| Bracelet and lug width | Beads-of-rice steel bracelet; NATO option; 20 mm lug width | Beads-of-rice steel bracelet; NATO option; 20 mm lug width |
| Displayed US price, checked October 8, 2026 | USD 2,190 | USD 2,890 |
Case diameter is identical, but the listed lengths and thicknesses differ slightly. Those measurements alone do not establish how either watch will fit a particular wrist; if possible, try one on and consider the complete watch, including bracelet, when assessing comfort.
Which Sea Emerald should you choose?
Choose the SUB 300T for its deeper rating and helium release valve
The SUB 300T is the model to consider if you specifically want DOXA’s higher published water-resistance rating, a helium release valve, or a bezel marked in feet. DOXA rates it to 120 ATM (1,200 m). That is the manufacturer’s stated rating; it should not be read as independent verification or a recommendation to take a watch to that depth. Its listed US price was USD 2,190 on October 8, 2026.
Choose the SUB 300 for the stated COSC certification and metric bezel
The SUB 300 is the option if explicit COSC certification on the product listing matters to you, or if you prefer a bezel scale in meters. DOXA lists its water resistance as 30 ATM (300 m), still a substantial manufacturer rating for a dive watch, but one quarter of the SUB 300T’s published depth figure. Its listed US price was USD 2,890 on October 8, 2026. The SUB 300T page gives movement specifications but does not make the same COSC-certification claim, so do not assume the two listings promise identical movement certification.
Rank #2
- NH35A Movement: The tactical frog watch is powered by the 24 Jewels NH35A self-winding movement, Assembled in Japan. Delicate and accurate.Power reserve can last for 41 hours.
- Cool Automatic Watch: Scratch resistant sapphire crystal glass with anti-reflective coating on inner surface; Stainless steel bracelet is adjustable by removing or adding links and fold over clasp with safety. A must have tactical frog watch for collection.
- Diving Watches: Double layer bezel design. Screw down lock for water tight seal and uni-directional outer stainless steel bezel to tell you "under" time easilly. Tactical frog mechanical watch is water resistant to 200M(20ATM). Suitable for professional marine activities, swimming, water sports and daily wearing.
- Luminated Watch: Green Luminious hands, scales and hour markers are featuring C3 material, which can last for at least 5 hours in dark and is able to quickly absorb and store light energy in a bright environment.
- Fashionable Style: The stylish outlook and vivid colored dial enhanced the sport and dynamic feel. A fashionable watch present for men, a must have for watch collection.
Bracelet, NATO option, and strap fit
DOXA lists both Sea Emerald models with a beads-of-rice steel bracelet and a NATO option. The SUB 300T US product page also shows straps and a clasp as separate accessories. Both models have a listed 20 mm lug width, but lug width alone does not confirm that a particular bracelet, clasp, end link, or strap will fit correctly. Match the accessory to the exact model and reference, and check the product listing or seller’s compatibility details before buying aftermarket hardware.
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What DOXA says about the SUB 300T’s history
DOXA’s SUB 300T Sea Emerald product page says the SUB 300T Conquistador launched in 1968 and calls it “the first general public diver’s watch equipped with a helium release valve.” This is DOXA’s historical claim, rather than an independently established conclusion here. Read DOXA’s account on the SUB 300T product page.
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.
