During the first few decades of recreational SCUBA diving, watch companies the world over did some of their best work.
In trying to cater to the adherents of this new and fascinating sport, they developed new technologies to better aid divers in keeping track of crucial information. One of the most critical pieces of information when diving is the number and length of “decompression stops” one must make before ascending. Though often relatively short and straightforward when engaged in recreational diving, these are essential for preventing the onset of decompression sickness — more commonly known as “the bends.”
The number and length of “deco” stops are governed by formulas that were once commonly available in the form of a table or guidebook. (These days, they’re self-contained within wrist-borne dive computers.) However, a handful of enterprising watch companies made “analog” computers long before the advent of the actual dive computer: In these special timepieces, the decompression scale was contained on the dial of the watch, formulated such that a diver could compute the number and length of decompression stops while underwater by glancing at his or her wrist.
While Mido’s Ocean Star Decompression Timer is perhaps the most famous such timepiece, another from Swiss brand Cornavin is equally fascinating. Furthermore, this particular example is in beautiful shape, with even patination and thick and even lugs. Housed in a 42mm stainless steel ‘stepped’ case with ‘holey’ lugs, an acrylic crystal, and an unsigned crown, it features a matte black dial with quadrant radium lume, a white decompression scale, an outer minute track, a rotating hour disc aperture — there’s no traditional hour hand — and a matching radium minute hand.
Calibrated in meters, the watch is powered by the Felso Calibre 810, an automatic movement securely hidden behind a screw-down caseback. By selecting one’s depth in meters and following the respective “track” around the dial, one can compute the required “deco” stop length given one’s bottom time. (Pretty neat!) Paired to an excellent leather strap from HODINKEE, it’s one of the most unique offerings we’ve been privileged to offer on Analog:Shift in quite some time.
It’s best to snag this one fast — as Harrison Ford once grumbled, “It belongs in a museum!”