The Rolex Sea-Dweller was designed with saturation divers in mind. Due to the use of helium in the gas mixture during saturation dives, helium particles would accumulate in diving watches during extended periods at depth, which would then escape through the weakest parts of a watch during decompression. It would often escape by popping the Plexiglas crystal off of the watch. Rolex developed the helium escape valve, built into the side of the watch case, to combat this issue and, therefore, allow for a safe release of the gas and continued reliability and durability of the watch.