Why is usually that important? If a unidirectional bezel is knocked and accidentally moved over a dive, it can only Exhibit a longer underwater time. That means the wearer will overestimate rather than underestimate immersion time, and in conditions that have to have decompression stops, this can be a make-it-or-split-it https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/