Where do the underwater bubbles come from when you shoot a bullet into water, or from a spinning propeller?

Question

In Saving Private Ryan there are scenes where the soldiers are underwater and bullets are shown going into the water with bubbles trailing behind them.

In films with submarines, the propellers often have bubbles coming out.

Where are these bubbles, or the air inside them, coming from?

In: 5

Answer 1

Not sure about submarines but most sterndrive and outboards (that I have seen/used) have thru-hub exhaust which would account for the bubbles you would see behind the prop.