My experience through talks with Robert-Jan Broer is his direct instruction from Omega that a person can swim with a 50-meter Moonwatch. This means surface swimming, not diving to 50 meters. Omega's confidence might or might not mean the 50-meter rating is a practical maximum depth - only that surface swimming is safe. The logical follow-up would be to consider whether the watch is tested to a depth beyond 50-meters either during the engineering phase or on an individual level before the watches leave the factory. Since most brands do NOT recommend swimming with a 50M watch, I've speculated that the Moonwatch or Omega watches generally are designed/tested beyond the rating on the caseback.