Think of what happens to a fluid when exposed to a vacuum.
The water surrounding the vacuum instantly vaporizes and creates bubbles of water vapor. Then these small vacuum bubbles collapse and create small shockwaves that create noise and damage the propeller/screw.
The water surrounding the vacuum instantly vaporizes and creates bubbles of water vapor. Then these small vacuum bubbles collapse and create small shockwaves that create noise and damage the propeller/screw.