Why is that important? If a unidirectional bezel is knocked and unintentionally moved with a dive, it may only Screen an extended underwater time. That means the wearer will overestimate instead of underestimate immersion time, As well as in situations that need decompression stops, This may be a make-it-or-crack-it variable https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/