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 pressurised 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. Divers breathe a mix of gases composed mainly of helium, whose extremely fine atoms can penetrate the case. On returning to the surface, the helium trapped inside can create a phenomenon of excess internal pressure liable to compromise its integrity.