Why is vital? If a unidirectional bezel is knocked and accidentally moved over a dive, it could only Display screen an extended underwater time. Which means the wearer will overestimate in lieu of underestimate immersion time, and in situations that call for decompression stops, this can be a make-it-or-split-it issue https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/