The Rolex Sea-Dweller was the first production Rolex diving watch to use the brand’s helium-release valve.
Rolex developed the Sea-Dweller for saturation divers, who sometimes lived and worked in pressurized underwater habitats. During decompression, helium atoms could enter a watch case. If pressure built up inside the case faster than it could escape, the crystal might be forced out.
The Sea-Dweller’s automatic helium-release valve allowed that internal gas to escape during decompression while keeping the case sealed during diving. Rolex introduced the model in 1967 after developing it with commercial divers, including workers associated with the French diving company COMEX.
The Sea-Dweller should not be confused with the Submariner, which was designed primarily as a conventional recreational and professional diving watch and did not originally use a helium valve. The later Deepsea extends the Sea-Dweller idea to much greater certified water resistance, but it was not the first Rolex model with the feature.