This is screw cavitation:
Cavitation occurs when the pressure on the forward face of the propeller blade becomes low enough that vapor bubbles form and the water boils. As the vapor bubbles pass over the blade face and move away from the low pressure area, they collapse. The collapsing of the vapor bubbles might seem trivial, but it is a very violent event which can result in the pitting of the propeller surface. Cavitation is a major source of propeller damage, vibration, noise, and loss of performance. Cavitation can be caused by nicks in the leading edge, bent blades, too much cup or simply high boat speed.
Whether or not screw cavitation occurs depends on: the shape and size of the screw, the speed at which it is turning, and how deep the screw is in the water.
To avoid generating cavitation-induced noise, modern submarines have large, slowly rotating screws and avoid high speed operations at shallow depths.
