At sea the half-hour was never read off a clock. It was struck on the bell, counting up in pairs. A ship's-bell clock for Apple Watch, iPhone and Apple Vision Pro.
Seven watches divide the day; the bell strikes every half hour, one to eight glasses, in paired strokes: one bell, two bells… eight bells.
Split so the pattern never repeats. The British convention resets the last dog watch to 1·2·3·8; Continental (5·6·7·8) is offered too.
Only one device rings at a time (wrist, pocket, or room), so you never get a wall of chimes.
Two- and three-watch crew rotations tell you when your team has the watch, on the dial, the widget and the complications.
Fire, Fog (COLREGs Rule 35) and the SOLAS General Alarm, each documented and sourced, none invented.
On Apple Vision Pro, a procedurally-made bronze bell you hang on a real wall, ring by hand, and hear in spatial audio.
Whichever device is the bell, the others keep quiet. A single, synced sound model runs across all three: which glasses ring, what they sound like, and which device rings them.