Why is always that vital? If a unidirectional bezel is knocked and unintentionally moved over a dive, it may possibly only display an extended underwater time. Which means the wearer will overestimate instead of underestimate immersion time, and in cases that need decompression stops, this can be a make-it-or-crack-it variable https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/