The IWC Aquatimer Automatic Ref. 812AD was IWC’s first true diver’s watch. Equipped with two crowns, one crown controlling the time and the other controlling the internal dive scale bezel — it made its public debut at the 1967 Basel Fair. The classic aesthetic still looks good today.

Almost five decades later, IWC Aquatimer Automatic is still making the Aquatimer. In fact, for 2014, the entire collection has been completely revamped. This review focuses on the base Aquatimer Automatic Ref. 3920, which is available in four variations. The dial still has the purist look and internal bezel, like its predecessor. Although, now the internal bezel is controlled via an external bezel, not a crown. This feature is very simple to operate, yet was incredibly difficult to engineer. It is the first of its kind and has been patented by IWC.

The IWC Aquatimer Automatic is a luxurious sports watch that looks just as good with a suit, as it does with a tank top and a pair of boardshorts. Ultimately, though, it is a dive “tool” watch, and accordingly, it needs to meet certain standards.

ISO 6425, a stipulated by the International Organization for Standardization, is a standard that requires that a true dive watch must: a) be water-resistant down to at least 100 meters b) feature a time controller c) comply with luminosity, shock resistance, anti-magnetism, and band solidity guidelines. All Aquatimers meet these requirements.

Uniquely, the entire Aquatimer line features the patented “SafeDive” external/internal rotating bezel. To operate it, you just rotate the external steel bezel like a normal dive bezel, and the internal bezel (or flange), which has the diving scale printed on it, automatically rotates in unison.

According to IWC, “For safety reasons, the internal rotating bezel can only be turned anticlockwise. This guarantees that even if the external rotating bezel is inadvertently moved, the dive time – during which the diver can return to the surface with no need for decompression stops – is not exceeded.”

A special sliding clutch, housed on the left side of the case, is key to this sophisticated system. There are a few potential downsides to such a complex system as opposed to a traditional bezel configuration: 1- the clutch housing protrudes on the left of the case 2- it is a proprietary system, and that typically costs more to fix.

I believe the upsides outweigh the downsides, as this is such a cool feature. And the housing did not cause me any discomfort on the wrist over the course of a week. Furthermore, the rotation feels both accurate and incredibly smooth. Definitely the best internal bezel system I have ever seen. Who wants to turn a crown to operate the internal bezel?