When the vapor bubble collapses, it can produce very large pressure spikes, which over time will cause damage on the propellor or turbine.

When a liquid boils, molecules of the liquid rapidly pass from the bulk liquid into vapor bubbles.

Because water is incompressible, collapsing vapor bubbles make a sharp, high, pressure spike at the moment they vanish.

This results in a vapor bubble forming.

What happens is that the water heats faster than the vapor bubbles can form.

In thermal inkjet printing, vapor bubbles are used as actuators.

As the surface temperature is increased, local boiling occurs and vapor bubbles nucleate, grow into the surrounding cooler fluid, and collapse.

These tubes provide an enormous surface area on which vapor bubbles can nucleate, and thus provides for excellent volitisation.

Possibly a few vapor bubbles might also form just inside the mouth of the bottle.

The inks used must have a volatile component to form the vapor bubble, otherwise droplet ejection cannot occur.