Why is that important? If a unidirectional bezel is knocked and accidentally moved over a dive, it can only Show a longer underwater time. Meaning the wearer will overestimate as opposed to underestimate immersion time, As well as in predicaments that involve decompression stops, this can be a make-it-or-break-it factor https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/