Requiring 18 months of research, development and testing to complete, the Hublot Oceanographic 4000 was the the first diver’s watch able to withstand the pressure exerted at a depth of 4,000 meters, or about 13,120 feet. (Hublot actually tested the seal all the way to 5,000 meters in a Roxer tank.) To ensure the watertightness of the watch and to resist this extreme pressure, the synthetic sapphire crystal is 6.5 mm thick. The screw-down caseback is made of grade 2 titanium. The Oceanographic 4000 has a helium valve, which allows gases that have infiltrated the watch during the descent to safely escape during the ascent.