Why is usually that critical? If a unidirectional bezel is knocked and unintentionally moved over a dive, it may only Show an extended underwater time. Meaning the wearer will overestimate rather then undervalue immersion time, and in cases that have to have decompression stops, this can be a make-it-or-split-it issue https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/