As a metallurgist, I found this post interesting. The pitting corrosion was most likely caused by salt water. All stainless alloys are susceptible to corrosion in salt water. Further, the anti-corrosion properties of these alloys rely on the presence of dissolved oxygen to form a protective coating on the surface, for instance as chromium oxide. Where the oxygen-bearing water is excluded, such as under rubber gaskets, the protective coating cannot form, and the corrosion will be exacerbated. The take-away from all this (i) don't expose your expensive watches to salt water & (ii) if you must, then rinse liberally with fresh water after exposure.