Due to the continuous development of deep diving by Comex, motivated by the potential securing of deep water oil & gas offshore contracts, Comex began a series of hyperbaric chamber testing to prove that it was humanly possible for divers to dive to extreme depths using helium. Another important risk factor was the newly discovered SNHP (underwater pressure syndrome), discovered by Comex in 1968, which caused divers uncontrollable trembling. At this stage, diving at those depths was still very much in its experimental phases and various scenarios were tested to try and curb those symptoms. Their first logical approach was to slow down the compression speed, but the symptoms were still very present, starting at 300m and becoming unbearable around 500 meters. The next stage was the development of breathing mixtures which consisted of mixing oxygen with hydrogen (used during the Hydra I and II experiments in 1968/1969, which is lighter and easier to breathe) but had the huge disadvantage of being explosive in presence of small amounts of oxygen and had a very unpleasant narcotic effect. The focus at that point shifted back to testing with helium which was the main element used in Physalie VI. The Physalie VI experiment was conducted in hyperbaric chamber in 1972 with the goal of testing human reactions under longlasting and increasing pressure while wearing the 1665 on their wrist as their tool watch. The two elite divers, Patrice Chemin and Robert Gauret, chosen for their previous record dives below 1600 ft, entered the chamber on May 18th and remained there until June 2nd 1972 (16 days). During that period they participated in various experiments (under the watchful eyes of the French CNRS scientific unit, several university scientific teams, the French Air Force and the Navy) testing the effects of the deep saturation dive, both in terms of physiological but also neurological aspects. Rolex, in cooperation with Comex, was still testing their watches and two 1665 Sea-Dwellers were given to the divers to be tested during the experiment. It is interesting to note that the depth achieved during this dive was 2000ft/610m, the same depth rating that was always on the dial of the 1665 Sea-Dweller. It is more than likely that despite having that depth rating since the first models in 1967, it was probably the first time that the model had been tested by humans at this depth. Following the huge success of this world record dive (that stood for 11 years) as well as an international advertising campaign, both divers were given a 1665 by Rolex, engraved with their names and record dive. This is an amazing opportunity to acquire the only two Double Red Sea-Dwellers that participated in a world record dive and were later donated by Rolex; they truly represent a crossover of what one could consider a double red Comex Sea-Dweller.