The Ultra-Technical Bühlmann Decompression 02 Dive Watch

There’s more to the dive watch category than your classic, 300m steel model with a rotating bezel. Some brands have long decided to pack dive watches with features that actually make sense underwater (and I’m not talking about a perpetual calendar here). So is the watch that we’ll be looking at today. As its name suggests, the Bühlmann Decompression 02 is the evolution of the Bühlmann Decompression 01. Imagined as a professional diving instrument, it is a high-tech dive watch, packed with features that go beyond your traditional dive watch. In particular, inspired by Albert Bühlmann’s original circular decompression calculator, it features 17 of the most frequent dive profiles and a “fly-no-fly” indicator.

Professor Albert A. Bühlmann (1923-1994) was a Swiss physician who was responsible for key research about decompression science at the University Hospital in Zürich. His impact on diving ranged from commercial and military diving to recreational diving. In particular, his ZH-L16 decompression algorithm is used to create decompression tables. Inspired by this legacy, Watch Angels launched the Bühlmann Decompression 01 in 2021, now evolved into the more elaborate Decompression 02.

A decompression table is a tool used by divers to plan safe ascents and avoid decompression sickness, which occurs when nitrogen absorbed under pressure forms dangerous bubbles in the body. It shows the maximum time a diver can spend at specific depths and, if exceeded, indicates where and how long decompression stops are required during ascent. While modern dive computers calculate this in real time, decompression tables remain a foundational safety guide, ensuring divers release nitrogen gradually and minimise the risk of injury.

A bold instrument-inspired case

Before diving (pun intended) into the watch-specific functionalities, the first thing that grabs your attention with the Bühlmann Decompression 02 is its technical look and commanding presence. Its distinctive three-crown case design is somehow reminiscent of 1970s bullhead chronographs. Constructed from stainless steel, it has a weighty, tank-like presence on the wrist. And at 48.5mm in diameter, it’s certainly not for the faint of heart. This isn’t a watch designed for the yacht club, but to match your diving suit. 

The three crowns are used respectively to wind the movement and set the time (centre crown), monitor the twin decompression dial (right-hand crown) and lock/unlock the twin decompression bezel (left-hand crown). The caseback is secured by 8 screws and is concave for enhanced wearing comfort. The case is inclined 5 degrees to ease legibility.

The Bühlmann Decompression 02 boasts a solid 575m water-resistance, a nod to Bühlmann’s record achieved in the Zürich hyperbaric chamber. With this rating, it’s fully prepared to follow you well beyond the 10-to-30-meter golden zone, the most enjoyable and safest depth range for recreational divers.

Designed as a professional diving instrument, the Bühlmann Decompression 02 features a helium relief valve integrated into the left-hand crown. Below a depth of 70 meters, air becomes toxic because of increased pressure. Divers who go this deep, by using diving bells or submersibles, breathe air that has been saturated with helium to prevent any risk of inert gas narcosis. Helium is one of the smallest elements; thus, it penetrates the watch where water cannot. During prolonged stays in a pressurised environment, the pressure inside the watch (initially surface pressure) gradually becomes the pressure of the diving depth. Depressurisation causes a problem when the diver ascends, or more precisely, returns to surface pressure. Without a helium escape valve, which enables the pressure to escape as soon as it reaches a certain level, the pressure may cause the crystal to pop out.

As you would expect for a proper dive watch, the Bühlmann Decompression 02 features a highly legible minute hand, which is the key information to monitor while diving. By contrast, the hour hand features a minimalist design. The seconds hand features a red, luminescent, arrow-shaped tip. As for all dive watches, its role is essential because it allows you to check that the watch is still running. If the watch stopped, even for a short period, it could give a false reading of elapsed time, which can be dangerous while managing decompression.

Twin decompression bezel and Twin Decompression Dial

Now that we have seen the basics, it is time to take a look at the specific functions of this dive watch like no other. The Bühlmann Decompression 02 is the first dive watch to feature what the brand calls the Bühlmann Twin Safety Bezel, a diving bezel that enables the separate tracking of the total dive time (TDT) and decompression stops (DS), each with its own blocking direction. The latter can be operated only when the 11 o’clock crown is released.

The decompression stop times for 17 dive profiles are featured on the Bühlmann Twin Dive Dial and are derived from Dr A. Bühlmann’s dive tables. The dive profile can be chosen by rotating the lower dial via the right-hand crown. The profile data and the related decompression stop time can be viewed and selected in the cut-out at 6 o’clock.

In effect, the total dive time bezel (inner bezel) is zeroed by aligning the 0 marker with the minutes hand when starting the dive. Once the bottom depth is reached, the chosen dive profile allows for monitoring the dive. When it is time to resurface, the ascent is monitored with decompression stops at 9m, 6m and 3m depth by using the outer decompression time bezel. 

The Decompression 02 focuses on the “Golden Zone” dive profiles with the 17 most common dive profiles for single-tank dives up to 39 meters depth, for dives at altitudes from 0 to 700m above sea level, as inscribed on the dial.

A rare function, at the end of the dive, the bottom dial is set to the “Fly-no-Fly” position and the corresponding indication is set to “no-fly” using the “date” setting position of the centre crown. An arrow points towards the red zone… It will be safe to fly once an arrow points to the green zone, once a minimum of 24-hour no-fly window is over (the “min” indicator means “check” as the date wheel might jump after 12 hours only).

Movement, Availability & Price

Inside the Bühlmann Decompression 02 is the tried and tested calibre SW-300. This clone of the ETA 2892 from Sellita measures 25.60mm in diameter, beats at 4Hz, with a minimum power reserve of 50 hours. The stop seconds mechanism allows for precise setting.

The Bühlmann Decompression 02 comes on a perforated rubber strap that, thanks to its design, allows for a wide range of adjustments. The buckle side of the strap is articulated, while the tail side is integrated into the lugs. The large, solid pin buckle is engraved with the brand’s logo. The watch is released in a limited edition of 575 pieces, and its price is set at CHF 3,990. It can be purchased exclusively on watchangels.ch.

A portion of each sale will be donated to the DAN Europe Medical Research Foundation to support its ongoing research into the perfect decompression algorithm.