Patek Philippe now offers the Aquanaut using a Men’s chronograph movement. This sporty complication fits perfectly in the company’s increasingly young, lively collection. However, how does it work in real-life ailments? We see in this comprehensive review from the WatchTime archives (first photographs by Patrick Mökesch).
Patek Philippe Aquanaut Men’s Chronograph – reclining

The collection was first established in 1997. Taking its inspiration in the Nautilus but with an upgraded, contemporary design and a rugged mix strap, it appeals to a young, sporty clientele. The CH 28-520 C caliber that compels the watch is almost 10 years younger still — the initial Men’s chronograph motion for its Nautilus-inspired watch with its rounded octagonal bezel.
The Aquanaut Men’s Chronograph, our test watch, has a stunning orange”Tropical” strap made of modern composite rubber that is resistant to wear, saltwater and UV rays, and can be combined with a new double folding clasp. With four separate catches and 2 side buttons, its patented design provides extreme reliability and simplicity of operation. It is attached using two spring bars at the strap finishes so the strap must be trimmed to the wearer’s individual wrist dimension — a strong movement that doesn’t allow for mistakes. And in case of a different event, Patek Philippe also provides the Aquanaut Men’s Chronograph using an additional black strap.

Fine adjustment uses four adjustable weights on the Gyromax balance wheel. The silicon hairspring is visible below.
The mechanics ticks beneath a threaded sapphire caseback and can be wound with a gold oscillating weight.
Self-winding Caliber CH 28-520 C ensures that a high level of accuracy, combining a traditional pillar wheel with a modern vertical-disk clutch control. It is the only chronograph movement at Patek Philippe with this kind of clutch. Its design prevents any forwards or backward leaping of the stopwatch hand once the chronograph is engaged and it runs so smoothly the professionally mounted chronograph hand can also be utilized as a permanent sweep seconds hand, which is why the Aquanaut Men’s Chronograph doesn’t have a separate seconds hand. The flyback function makes it feasible to set the watch just, to the second. The stopwatch hand can be put to zero from an ongoing measurement with no reset and restarted immediately. Obviously, this also works by beginning the chronograph just at a time signal. The only downside: that the motion has no hack mechanism so that it may be required to reset the minutes hand.

Caliber CG 28-520 C has experienced some design changes for use from the Aquanaut. The hour counter has been omitted completely. However, what young, lively person today wants such a thing? Elapsed minutes are easy to read on the big subdial counter, because it extends almost to the middle of the dial and is instinctive — that the 60-minute counter mirrors the conventional minutes screen on a watch dial (rather than a more commonly used 30-minute counter). A minute counter wheel rotating beneath functions with an immediate transmission ratio to the chronograph runner, which allows the elapsed minutes screen to run continuously and does not jump when the second hand moves”zero.”

This mechanism is placed on the dial side of the chronograph.