Seiko have long been the masters of the accessible dive watch game, dominating with one of the most extensive ranges of sub £2k divers of any brand. From the Sumo to the Turtle, to the most recent PADI collection, there have been quite literally hundreds of references over the years. But in all that time there’s never been a mechanical Seiko Diver GMT, until earlier this year with the launch of the limited edition SPB385J1. Now that watch has been reimagined as the non-limited Prospex GMT Diver Marine Green and Dark Depths.
The watches have 42mm cases with large diving bezels, facetted lugs and a crown positioned at 4 o’clock. To be honest, describing the new watches in plural is a slight misnomer because they’re the same watch, it’s just that one has a green dial and the other is black. Hence the names Marine Green and Dark Depths.
As for the display, it’ll be familiar to any fans of the Prospex diving range because it has the signature circle, rectangle and shield shaped hour markers, all coated with lume for low light legibility. The major difference is the addition of a 24-hour scale on the watch’s flange – the portion of the display that connects the dial to the crystal above and which is sometimes used as an internal bezel.
The 24-hour scale corresponds to the central GMT hand to display the time in a second time zone. Not a terribly useful complication while you’re underwater but one that makes sense for those who travel across the world to visit all the best diving destinations. Or those who just enjoy the travel with no intention of going near the water since it only has 200m water resistance.
In order to include the GMT function, the Prospex GMT Diver Marine Green and Dark Depths house the new 6R54 automatic calibre with a 72-hour power reserve. That power reserve is impressive given the price, although the accuracy rating of -15/+25 seconds per day could be better. Speaking of price, both colourways are priced at £1,400.


That might seem pricey for a Seiko diver but it’s worth considering that it has an additional complication compared to the majority. Plus, the previous limited edition was priced £1,600. To my mind, these watches are yet more proof that Seiko is one of the trendiest watchmakers of the moment.
Price & Specs:
- Model: Seiko Prospex ‘Dark Depths’ and ‘Marine Green’ GMT Diver
- Ref: SPB381J1 (Marine Green), SPB383J1 (Dark Depths)
- Case/dial: 42mm diameter x 12.9mm thickness, stainless steel case, black or green dial
- Water resistance: 200m (20 bar)
- Movement: Seiko calibre 6R54, automatic
- Frequency: 21,600 vph (3 Hz)
- Power reserve: 72h
- Functions: Hours, minutes, seconds, date, GMT
- Strap: Stainless steel bracelet
- Price/availability: £1,400
More details at Seiko Boutique.
I find the “since it ‘only’ has 200m water resistance” statement somewhat insignificant, here – implying that 200m isn’t more than adequate for 99.9% of divers? The advanced certification from PADI only permits a depth of 30 metres. Advanced! Nevertheless, nice article.