Rolex launched the Oyster Perpetual Sea-Dweller in 1967 to address the challenges of working underwater for long periods of time. The brand then worked closely with experts from French diving company Comex (Compagnie Maritime d'Expertises) to improve the device, and the watch is now waterproof to a depth of 1,220 meters (4,000 feet). Sea-Dweller is designed for saturation diving. Its helium discharge valves control the decompression process of ascent and return to the surface to help complete the final phase of deep-sea exploration.