The Essential Guide to Water Resistance in Watchmaking

An automatic movement ensured the seals would not be worn out by winding via the crown. The hacking seconds was useful to synchronise time in a group, and furthermore, Blancpain designed a case back with a channel designed to fit the rubber ‘O’-ring, supported by an additional metallic disc to fix its position. Fiechter’s invention came at the perfect time: Captain Robert Maloubier, founder of the French Combat Swimmers team, was looking for a utility watch that could do exactly what the Fifty Fathoms offered.

In 1968, the COMEX diving organisation developed a hyperbaric chamber that could be used to test water resistance accurately. Various brands partnered with COMEX to develop solutions for deep water diving purposes, as submersibles designed to explore the deep blue were produced. OMEGA was one of the watch companies working towards this, and the result was the Seamaster Ploprof, short for Plongeurs Professionel, or Professional Divers.

The original Ploprof had a measured resistance to 600 metres of depth, and featured a large pusher locking system for the bezel. Most importantly, it had a fully monobloc case to simplify the protection against water penetration. Today, the Ploprof comes in O-Megasteel or titanium, and it has a depth rating of 1,200 metres. The titanium model has a mesh-style, shark-proof strap. In case of an attack, fling the Ploprof at the shark and swim away. Hopefully, it’s distracted by the movement of the watch and has its teeth trapped by the bracelet.

Piquerez was also responsible for one of the biggest innovations in water resistance history. In the late ’60s, Erwin Piquerez collaborated with Jack Heuer to develop a statement-making watch case, to match Heuer’s pursuit of the automatic mechanical chronograph. The case maker’s success was exclusively offered to Heuer, and on March 3, 1969, the Monaco Ref. 1133B was presented at Baselworld with the Calibre 11 housed within.

In 1990, the International Organisation for Standardisation (ISO) set guidelines for water-resistant timepieces, prohibiting ‘waterproof’ in official specifications. ISO 2281:1990 or its German DIN equivalent, 8310, specifies testing procedures that include overpressure, and resistance of the watch overall as well as operative parts.

Six years later, ISO 6425 became a standard for diving timepieces, and it remains the definitive standard for water resistance where watches must have a minimum of 100 metres and must offer water resistance of 125 percent of the stated value. For example, the Pelagos Ultra which TUDOR released at Watches and Wonders Geneva this April, will need to be tested for a water resistance of 1,250 metres in order to earn its rating. The requirement is a safety failproof designed to minimise the potential of equipment failure in critical moments.

The pursuit of ultra-deep diving watches took off in the early eighties, with watchmakers like Breitling introducing their own version on the Superocean collection. The M2000 model had a very thick case design, in order to withstand the pressure the watch faced at great depths. These were intended for professional use, like its Navitimer models. They were not the only ones that were targeting professional audiences for high depth rating watches.

And even though Grand Seiko isn’t setting ultra-deep records, its professional diving watch uses corrosion-free titanium with the calibrre 9RA5. The 5-day power reserve of the movement, along with the Spring Drive mechanism’s renowned precision, makes this one of the most all-rounded diving watches today.