Why is usually that vital? If a unidirectional bezel is knocked and accidentally moved on a dive, it might only Screen a longer underwater time. Meaning the wearer will overestimate instead of underestimate immersion time, and in scenarios that have to have decompression stops, This may be a make-it-or-break-it issue https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/