The Aquanaut is a relatively young collection for Patek Philippe. The first generation, Ref. 5060, debuted in 1997 as a little brother to the Nautilus. From that point on, the series progressed to the second generation, 5065 (1998), and then to the current generation, 5167 (2007). The one we have here for review is the Ref. 5168 (2017 onwards), which is dubbed Jumbo, a larger version of the current generation Aquanaut.

This watch was introduced at Baselworld 2019 with a 42.2mm case in 18K white gold, khaki green dial, and rubber strap. Considering that the original 5060 is 35mm, the 5065 is 38mm (aka “Large”), and the current 5167 is 40mm, there is no doubt this “Jumbo” is a watch with some serious presence. I think it reflects Patek Philippe’s positioning of the Aquanaut as a sportier collection in its catalog. For Patek Philippe, 42.2mm is one of the largest watches, and only rivaled by the Calatrava Pilot Travel Time, Flyback Chronograph Annual Calendar (both 42mm), and the Celestial (44mm), which is a Grand Complication.

The big brother Nautilus is staying at 40mm, and even its annual calendar with moon-phase and chronograph-equipped variants are kept at the 40.5mm mark. The Aquanaut is clearly positioned within the luxury sport watch category. By the way, there is also a complication-equipped variant, the Aquanaut Ref. 5968A Automatic Chronograph, which shares the “Jumbo” case.

The khaki green color is undoubtedly the most notable thing about this Aquanaut, and it is a quite unusual colorway for Patek Philippe. The tone isn’t vivid, and I think this matte khaki green is a versatile choice in the green dial trend. The tropical rubber strap is a slightly deeper khaki green compared to the dial, but it maintains a similar tone. Although the khaki green color is best known for its military origin, Patek demonstrates it can be quite refined. I think the octagonal bezel and the iconic porthole-inspired case design are responsible for that effect. I suppose a really great watch can wear any color (like the special red themed 5167A for the Singapore Grand Exhibition last year, for example) because the color actually enhances the fundamental character of the watch instead of muddying it up.

Even though the watch has a case diameter of 42.2mm, its extremely thin profile of 8.25mm coupled with a highly integrated rubber strap ensures a very light fit on your wrist. The lugs are designed to flow out of the case, but their stubby and sporty shape has a clear intent and purpose. Especially during the summer season, I think you could pull this off with a business casual outfit depending on your work environment (if you are telecommuting like many of us right now, you don’t even have to worry about that).

I was surprised by the quality of the buckle on this watch. The main plate that touches the wrist also acts as the release button, enabling the whole buckle to be extremely compact. This construction was made possible by the plate having a springy tension (not mechanically spring-loaded), and that contributes to not only the wearing comfort but also a very smooth open-close action. Typically, your fingers would feel a resistance when you press the release buttons to undo the buckle. You’ll notice next to no stress to your fingertips operating the buckle of this Aquanaut. These kinds of details really show off Patek Philippe’s quality.

The highly wearable thin case design was made possible by the Cal. 324 S C movement. This caliber made its debut in 2004, and it has since become a classic automatic powerhouse that’s also used as the foundation of many other Patek Philippe movements. We often talk about thinness as a sign of quality in mechanical watchmaking, and Patek Philippe was able to come up with this masterpiece based upon its long history in this field. There are several significant design efforts in the Cal. 324 to reduce the thickness, such as offsetting the second wheel that often interferes with the winding rotor, and the third wheel driving the second pinion at the center of the movement instead of the fourth wheel running the seconds hand, which is more typical.

This caliber further shaves the thickness by placing the automatic rotor drive train on the same layer as the hand-winding mechanism and other trains. To make that happen, you’d have to design each train as efficiently and compactly as possible. The Aquanaut Ref. 5168 might be, categorically speaking, a simple 3-hander with date, but the watch packs a tremendous amount of attention to detail that is simply unmatched by most watches out there.

For this review, we focused on this rather rare khaki green Patek Philippe, but let’s think about the Aquanaut’s role before closing. I believe the watch aims at something very different from the Nautilus, which is often categorized in the same genre as the Aquanaut. When I think about the target audience, I think the Nautilus is aimed at the existing customer base, while the Aquanaut is meant for a brand-new clientele. The Aquanaut is exploring important factors such as colors and sizes, and for Patek Philippe, the watch is aimed at the brand-new customer base that defines the future.

Patek Philippe Aquanaut “Jumbo” 5168G-010 Khaki Green: 42.2mm case diameter (across 10 to 4 o’clock), 8.25mm-thick; 18K white-gold case with display caseback. Movement: Cal. 324 S C, 4Hz (28,800 vph), automatic with 35-hour (mini.) to 45-hour (max.) power reserve; Spiromax hairspring, Gyromax balance. Stamped with the Patek Philippe Seal. Functions: hours, minutes, seconds, date. 12 ATM water resistance. Khaki green composite material strap. Price: $39,690