Rolex created the Oyster Perpetual Sea‑Dweller in 1967 to meet the challenge of prolonged underwater missions. Subsequently improved in close partnership with Comex (Compagnie Maritime d'Expertises) professionals, it is now waterproof to 1,220 metres (4,000 feet). The Sea‑Dweller is specifically designed for saturation diving. Thanks to its helium escape valve, it can withstand decompression on ascent and master the return to the surface – the final phase of deep-sea exploration.

In the 1960s, so-called “saturation” diving made it possible to remain at great depths for extended periods. It consists of housing divers in a pressurized habitat, so as to reproduce the pressure that prevails in their underwater working environment. This means that they need only undergo a single decompression process, at the very end of the mission.

This process can damage the watch. The divers breathe a mix of gases composed mainly of helium, whose extremely fine atoms can penetrate the case. On returning to the surface, the trapped helium can create a phenomenon of excess internal pressure liable to compromise the integrity of divers’ watches.

In order to overcome this problem, in 1967 Rolex introduced the Sea‑Dweller, a divers’ watch with a helium escape valve. This unique safety valve opens automatically when the internal pressure in the case is too high, allowing the helium atoms to escape.

The number of undersea missions increased from the 1960s onwards, and they took on a new format. Divers were now not only faced with longer immersion times during saturation dives, but also with diving to greater depths. The professional watches designed for them therefore needed to be able to withstand ever-increasing pressure.

Guaranteed waterproof to a depth of 610 metres (2,000 feet) when it was launched in 1967, then to 1,220 metres (4,000 feet) from 1978, the Sea‑Dweller combines all the attributes of the modern divers’ watch.

Tested in real-life conditions as part of the Tektite programme, initiated jointly by NASA, the US Navy and the US Government in 1969, the Sea‑Dweller accompanied the first major experiments with underwater habitats.

In 1971, Rolex formalized its exclusive partnership with Comex, with the Sea‑Dweller used by its divers, who hold numerous world records. The French company, which specializes in underwater engineering, technology and intervention, develops hyperbaric simulation chambers that are used to improve training for oceanographic researchers, fighter pilots and astronauts.

As an extension of this partnership, Comex works with Rolex to design and develop the hyperbaric tanks used for the waterproofness tests carried out as part of the Superlative Chronometer certification process. These tanks are used to test the watches' resistance to depths of up to 13,750 metres (45,112 feet), as is the case for the Deepsea Challenge, a divers’ watch for extreme depths.