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> A watch rated at 15 bars will then resist to 15 atmospheres witch is 140
> meters(1 atm at surface).

Nope.  This is a nitpick, but a watch rated at 15 bars means 15 bars of
differential pressure (inside to outside of casing).  So you don't need to
add that "1 atm at surface".  At the surface, the watch is experiencing

Terho>	That is 15 bar total pressure difference. However, the
	total difference consists of two parts; static pressure
	from the depth and dynamic pressure from the movements
	of the clock. While in water, by moving your hand quickly
	it is fairly easy to get several bars of dynamic pressure
	which must be removed from the total rating giving lower
	static (depth) pressure. That's why so many diver's
	watches are rated to 200 meters (20 bar) giving enough
	headroom above the static pressure due the movements.

	So, by saying that a watch is rated to 15 bars overpressure,
	you can not give any specific depth equal to the pressure
	because you are moving the watch at different speed and
	directions in water. But it still gives a figure what
	depth range we are talking.

	Terho

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