Regarding to Conservation of Energy(Bernoulli's equation)
Energy of velocity＋Energy of pressure＝Constant
Pressure decreases with increase of velocity.
At high altitude, decreasing of atmospheric pressure decreases boiling temperature.
High-speed flow induces decrease of pressure, and then "boiling" takes place at room temperature.
Namely, water became bubble at room temperature at high-speed flow.

Boiling: Water becomes vapor by heat up.
Cavitation: Water becomes vapor by increase of velocity, i.e. decrease of pressure.

Cavitation is developed from cavitation nuclei such as tiny bubble at high-speed region.
Shock wave and/or micro jet is produced, when cavitation bubble is collapsed at low speed
region. Shock wave and/or micro jet takes places plastic deformation.