Why is that essential? If a unidirectional bezel is knocked and accidentally moved on a dive, it could only Display screen a longer underwater time. Meaning the wearer will overestimate rather then underestimate immersion time, As well as in cases that involve decompression stops, this can be a make-it-or-split-it variable https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/