The Ulysse Nardin Diver [AIR] is the World's Lightest Mechanical Dive Watch

For its previous two outings as an exhibitor at Watches & Wonders Geneva, Ulysse Nardin has focused on expanding and updating its most off-the-wall collection, the Freak. For 2025, the Le Locle-based maison shifts gears back to its historical, nautical roots while still keeping firmly to its modern path as an innovator in technology and materials. The result is nothing less than one of the talking-point timepieces of the entire exhibition, the new Diver [AIR], a skeletonized iteration of the brand’s Diver model, which takes the title of the world’s lightest mechanical dive watch.

As I explore much more thoroughly in this article, Ulysse Nardin is a brand whose association with seafaring and ocean exploration goes back much further than most. It gained worldwide acclaim for making some of the earliest and most accurate marine chronometers, supplying them to many of the world’s navies throughout the 19th and early 20th centuries. It made its first waterproof instrument in 1893 and its first dedicated wristwatch for diving in 1964. More recently, Ulysse Nardin made the bold move of combining the robustness and functionality of a dive watch with the high-horological savoir-faire of a skeletonized movement in 2021’s Diver X Skeleton, a breakthrough timepiece that would become the most direct antecedent of the new Diver [AIR]. The Diver X skeleton weighed only 105.8 grams, a full 15 grams lighter than the 120.5 grams of the standard Ulysse Nardin Diver 44mm in titanium. The Diver [AIR] slashes the weight even further, by more than half, to an astonishing 52 grams, including the strap. The watch manages this feat with a clever combination of material choices and innovative micro-engineering. 

Like the Diver X Skeleton, this watch has a severely stripped-down movement, here with even more material removed, leaving behind a space inside the case that is approximately 80 percent air and 20 percent solid material — hence the model’s name. Ulysse Nardin’s engineers formed the slender, hollowed-out bridges into triangular shapes to ensure rigidity and resist bending and warping — a trick used in architectural design — and minimized the rotor to its essentials. They also reconfigured the mainspring barrel into a flying arrangement to reduce the mass of its top bridge and carved material from the barrel itself to lighten it further. All told, the entirety of the new Caliber UN-374 weighs a wispy 7 grams — less than half the weight of the Diver X Skeleton’s movement. This is despite the fact that the most obvious method of removing weight from a watch movement — dispensing with the rotor and its self-winding capability completely — was not considered here. Why? Because this is still, in the final analysis, supposed to be a watch to dive with, and an automatic movement is a requirement that a dive watch must meet. 

The key material used in the movement in titanium, prized for its strength and lightness and rarely used in this particular area of watchmaking because of its difficulty to manipulate and its tendency (and this is something I just learned) to catch fire during machining. Titanium is also the material of choice for the 44mm case, along with carbon fiber, another lightweight and sturdy material found in the motorsport and aerospace industries. The cutting-edge combination makes for a case that is water-resistant to 200 meters. Continuing in the eco-friendly tradition established with another of the brand’s high-concept dive watches, 2020’s Diver Net, 90 percent of the titanium in this watch’s construction is recycled and sourced from the Swiss biomedical industry. The carbon fiber used for the case’s side panels is a variety called Nylo-Foil, partially recovered from used ocean netting, which is lighter than traditional carbon fiber. The luminous insert on the watch’s unidirectional rotating bezel (again, we’re talking a “real” dive watch here) is made from CarbonFoil, made of 100-percent upcycled carbon fibers and compressed to form the unique marbled pattern on its surface. As with most every Ulysse Nardin watch in the 21st Century, silicon also plays an important role, with the friction-free, antimagnetic material used for the escapement, which supplies the movement with a lengthy power reserve of 90 hours.

Even the straps of the Diver [AIR] have been chosen with lightness and sturdiness in mind; each watch comes with two ultralight, elasticized fabric straps — one in white, the other orange — that fasten with a scratch closure and can be easily swapped without tools. The price is $38,000.