What time is it? Watches and horology

There are some use cases that prefer a countdown bezel to a count-up one. For general diving use the count-up is pretty ubiquitous, but for certain use cases a countdown is preferred. Usually it’s on pilots watches for timing turns, navigation etc. but you also see it on some other watches made for military purposes. They are used to synchronise mission events. Eg (hypothetically given how obsolete this tech is) you might be tracking time remaining to get into position for a coordinated manoeuvre.