IWC Schaffhausen Aquatimer Split Minute Chronograph Mode D'emploi page 25

Marking the start of a dive
Turning the reset button in a clockwise direction causes the bezel inside
the case to rotate, enabling the triangle on the bezel to be aligned with the
minute hand. The desired time (start of the dive) can be set in this way.
You can read the elapsed time (duration of the dive) on the bezel. For safety
reasons, the bezel can only be turned in the anti-clockwise direction. The
audible and sensible indexing takes place in steps of one minute. The bezel
is also visible in the dark thanks to its luminous markings.
Use of the watch as a timer when diving presupposes the appropriate
diving training and regular testing of the water resistance of the watch.
Operating the Split Minute function
The Split Minute function permits the measurement of a time to the nearest
minute (for example the duration of a decompression stop during a dive)
and is operated by the rocker switch on the case. The position of the rocker
switch indicates whether the Split Minute hand is running synchronously
with the minute hand (0) or has been stopped (I).
Split Minute function – Off (0)
Minute measurement is disengaged, and the Split Minute
hand runs synchronously with the minute hand.
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