Seeing a brand like De Bethune — a technical powerhouse whose case architecture and movement design hovers in the realm of sci-fi futurism — enter the dive watch category is something that few really saw coming. Yes, its predecessor the DB28GS is technically a sports watch, and one with a resilient and shock resistant movement, but these earlier watches were far more focused on surviving your average daily living. With the launch of the Grand Bleu in 2019, the brand’s efforts were steered in a much more focused and purposeful direction. Being a true dive watch means a number of factors are in play here. A unidirectional timing bezel is fitted, though its design is an effective split between the typical inner and outer timing bezels seen on conventional dive watches. While it is operated by its knurled outer ring, the timing track of the bezel insert is located below the timepiece’s sapphire crystal. Though the 105 meters of water resistance was inspired by Luc Besson’s film, Le Grand Bleu, the figure is also quite likely limited by this bezel design. With the crystal affixed to the bezel itself, an additional set of gaskets running the perimeter of the case are likely a prohibitive factor for increasing its depth capabilities.
Bright Ideas
This is of course is but the tip of the iceberg when it comes to necessary dive watch specs. Proper legibility in poor light is always a necessity, and De Bethune took not one but two separate approaches to solving this matter effectively. First, they enlisted James Thompson of Black Badger to develop a proprietary luminous compound that matches the blued titanium used on the Grand Bleu’s hours and minutes hands. This compound is used on the timing bezel as well as the fixed minutes track, alongside a white compound that is applied to the tips of the hands. For most dive watches this would be plenty effective all on its own, but De Bethune decided to take things an extra step further.
To put things simply, “take G-Shock backlighting and make it high-end and mechanical” is the less-than-technical way of describing where De Bethune went with the Grand Bleu. By taking the principle of a dynamo — a mechanical power-generating device that converts mechanical energy into electrical energy — and scaling it down to a micro level, the watch movement itself is able to power four small LED lights located at 3, 6, 9, and 12 o’clock. The power is unpacked from one of Calibre DB2080’s mainspring barrels, and as its wearer presses the activation button at 6 o’clock, a separate geartrain is activated to provide power and activate the lighting system. It’s worth noting here that this does somewhat drain the overall power reserve of the watch, and that when the 5-day power reserve is down to its last day, the lighting function is suspended in order to maintain running accuracy.
Now, this wouldn’t be a De Bethune without some impressive trickery lurking in its inner workings. The DB2080 was an all new calibre developed specifically for the Grand Bleu, which is no surprise given the aforementioned lighting setup, although the latter is not the calibre’s only special trick. First, you’ll note the use of a titanium balance wheel with white gold poising weights, suspended from a titanium-polished bridge. The aforementioned bridge has its own pare-chute shock absorbers on either end, as well as a shock absorber for the balance wheel itself.
The balance of the calibre remains visible, as one comes to expect from the brand. The brand’s trademark “shield” bridge provides a large surface area for a mix of ribbed and polished finishes, though off to the right you’ll note an added bit of gearing — the governor and other associated gearing that manages the lighting system. At a functional level, the brand threw the industry a bit of a curveball with this calibre. by deciding to add a deadbeat seconds complication to the mix. It’s an unorthodox choice for a diving model, to say the least.
For many, one of the big selling features of the DB28GS Grand Bleu will be the case design . De Bethune’s floating lug system is a beautiful thing, and even at 44mm in diameter, these watches fit extremely well on a wide range of wrist sizes. Unlike most DB28 variants that are built with titanium cases, the Grand Bleu, has a central case barrel in black Zirconium, sandwiched between a titanium bezel and caseback. Being a slightly thicker case, measuring 12.8mm thick, this use of contrasting material gives the caseband a touch more visual character, however the material is effectively equivalent to titanium in strength, weight, scratch resistance, and other notable factors.
Arguably the most unorthodox and unexpected dive watch of the 21st century, if not in the history of watchmaking, you have to hand it to the brand for their ability to stick to their guns and design a watch that in no way panders to the specificity of the dive watch category.
This year GMT Magazine and WorldTempus have embarked on the ambitious project of summarising the divers watch since 2000 in The Millennium Watch Book - Divers watch, a big, beautifully laid out coffee table book. This article is an extract. The Millennium Watch Book - Divers watch is available in both French and English here:
Written by Justin Mastin-Frost
